# Iterative deepening depth-first search (IDS) Source Code Program

/********************************************************************************************************
IDS Normal Works For Directional
*********************************************************************************************************/

#include <iostream>

#include <string>

#include <map>

#include <queue>

#include <stack>

#include <algorithm>

#include <list>

#include <set>

#include <cmath>

#include <cstring>

#include <stdio.h>

#include <string.h>

#include <sstream>

#include <stdlib.h>

#include <vector>

#include <iomanip>

using namespace std;

#ifdef __GNUC__

typedef long long ll;typedef unsigned long long ull;

#else

typedef __int64 ll;  typedef unsigned __int64 ull;

#endif

#define inf (1<<30)-1

#define SIZE 10001

#define pi (2*acos(0.0))

#define forn(i,n) for (i=0;i<n;i++)

#define forr(i,n) for (i=n-1;i>=0;i--)

#define forab(i,p,k) for (i=p; i<=k;i++)

#define FOREACH(it,x) for(__typeof((x).begin()) it=(x.begin()); it!=(x).end(); ++it)

#define bug(x)    cout<< "->" <<#x<<": "<<x<<endl

#define Sort(x) sort(x.begin(),x.end())

#define Reverse(x) reverse(x.begin(),x.end())

#define mp(a,b) make_pair(a,b)

#define zero(x,with) memset(x,with,sizeof(x))

#define copy(c,r)   memcpy(c,r,sizeof(r))

#define sz(x) (int)x.size()

#define length(x) (int)x.length()

#define all(x) x.begin(),x.end()

#define pb push_back

#define popcount(i) __builtin_popcount(i)

#define gcd(a,b)    __gcd(a,b)

#define fs first

#define sc second

#define two(X) (1<<(X))

#define twoL(X) (((int64)(1))<<(X))

#define contain(S,X) (((S)&two(X))!=0)

#define containL(S,X) (((S)&twoL(X))!=0)

#define maxi(v) *max_element(all(v))

#define mini(v) *min_element(all(v))

#define CS c_str()

#define clr clear()

#define err 1e-9

#define even(a) ((a)%2==0)

#define odd(a) ((a)%2==1)

#define WHITE 0

#define GRAY  1

#define BLACK 2

#define NIL 0

typedef pair<int,int> pii;

typedef pair<double,double> pdd;

typedef vector<int> vi;

typedef vector<double>vd;

typedef vector<ll>vll;

typedef vector<string> vs;

typedef vector<vi>vvi;

typedef vector<vll>vvll;

typedef vector<vd>vvd;

typedef vector<pii>vpii;

typedef map<string,int> msi;

typedef map<int,int>mii;

typedef map<pii,int>mpi;

template<class T> inline T gcd(T a,T b) {if(!b) return a; else return gcd(b,a%b);}

template<class T> void b_sort(vector<T>& VT) {for(int i=VT.sz;i>0;i--)for(int j=1;j<i;j++)if(VT[j]<VT[j-1]) swap(VT[j],VT[j-1]);}

template<class T> inline T sqr(T x){return x*x;}

template<class T> inline bool isprime(T n){if(n<=1)return false;for (T i=2;i*i<=n;i++) if (n%i==0) return false;return true;}

template<class T> inline T mod(T n,T m) {return (n%m+m)%m;} //For Positive Negative No.

template<class T> string tostring(T n){ostringstream oss;oss<<n;oss.flush();return oss.str();}

int toint(string s){int r=0;istringstream sin(s);sin>>r;return r;}

ll toll(string s){ll r=0;istringstream sin(s); sin>>r; return r;}

template<class T> void debug(const T& e){cout<<e<<endl;}

template<class T1,class T2> void debug(const T1& e1,const T2& e2){cout<<e1<<"\t"<<e2<<endl;}

template<class T1,class T2,class T3> void debug(const T1& e1,const T2& e2,const T3& e3){cout<<e1<<"\t"<<e2<<"\t"<<e3<<endl;}

template<class T1,class T2,class T3,class T4> void debug(const T1& e1,const T2& e2,const T3& e3,const T4& e4){cout<<e1<<"\t"<<e2<<"\t"<<e3<<"\t"<<e4<<endl;}

template<class T1,class T2,class T3,class T4,class T5> void debug(const T1& e1,const T2& e2,const T3& e3,const T4& e4,const T5& e5){cout<<e1<<"\t"<<e2<<"\t"<<e3<<"\t"<<e4<<"\t"<<e5<<endl;}

template<class T> void debug(vector<T>& e){int i;forn(i,sz(e)) cout<<e[i]<<" ";cout<<endl;}

template<class T> void debug(vector< basic_string<T> >& e){int i,j;forn(i,sz(e)) {forn(j,sz(e[i])) cout<<e[i][j];cout<<endl;} cout<<endl;}

template<class T> void debug(vector< vector<T> >& e,int row,int col){int i,j;forn(i,row) {forn(j,col) cout<<e[i][j]<<"\t";cout<<endl;} cout<<endl;}

template<class T> void debug(T e[SIZE][SIZE],int row,int col){int i,j;forn(i,row) {forn(j,col) cout<<e[i][j]<<" ";cout<<endl;}}

inline bool iseq(double x,double y){if(fabs(x-y)<err)return true;return false;}

template<typename T>inline T bigmod(T b,T p,T m){if(!p)return 1;else if(!(p%2)){T x=bigmod(b,p/2,m);return x*x;}else return ((b%m)*bigmod(b,p-1,m))%m;}

ll Pow(ll B,ll P){  ll R=1;  while(P>0)  {if(P%2==1)  R=(R*B);P/=2;B=(B*B);}return R;} //compute b^p

//struct pq{    int cost,node;bool operator<(const pq &b)const{return cost>b.cost;}};// Min Priority Queue

//typedef struct {     int x,y; }st;

//st XX[100];

//bool comp(st a,st b){    return a.x > b.x;}   //Comp Sort

//int dx[]={1,0,-1,0};int dy[]={0,1,0,-1}; //4 Direction

//int dx[]={1,1,0,-1,-1,-1,0,1};int dy[]={0,1,1,1,0,-1,-1,-1};//8 direction

//int dx[]={2,1,-1,-2,-2,-1,1,2};int dy[]={1,2,2,1,-1,-2,-2,-1};//Knight Direction

int parent[SIZE],color[SIZE], Time, f[SIZE], cost[SIZE] ;

int DLS(int node, int goal, int depth)

{

int i,x;
if ( depth >= 0 )
{
if ( node == goal )
{
return node;
}
for(i=0;i<nodes;i++)
{
{
child = i;
x = DLS(child, goal, depth-1);
if(x == goal)return goal;
}
}
}
return 0;
}

int IDDFS(int root,int goal)

{

depth = 0;solution = 0;
while(solution <= 0 && depth < nodes)
{
solution = DLS(root, goal, depth);
depth++;
}
if(depth  == nodes)return inf;
return depth-1;
}

int main()

{

int i,u,v,source,goal;
freopen("IDS.in","r",stdin);
while(scanf("%d%d",&nodes,&edges) == 2)
{
for(i=0;i<edges;i++)
{
scanf("%d %d",&u,&v);
//adj[v][u] = 1;//For Bidirectional Active this line
}
scanf("%d %d",&source,&goal);
for( u = 0; u <= nodes; u++ )
{
color[u] = WHITE ;
parent[u] = NIL ;
cost[u] = inf;
}
Time = 0 ;         depth = IDDFS(source,goal);         if(depth == inf)printf("No solution Exist\n");
else printf("Solution Found in depth limit ( %d ).\n",depth);
}
return 0;
}