// Author := Abhishek Giri

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back]
#define pii pair<int,int>
#define pll pair<ll,ll>
#define mp make_pair
#define mod (ll)1e9 + 7
#define V(type) vector<(type)>
#define in(var) cin>>(var)
#define out(var) cout<<(var)
#define on(var) cout<<var<<"\n"
#define f(i,n) for(ll i = 0 ; i < n ;i++)
#define mfor(i,init,n,b) for(ll i = (init) ; i < (n) ; i+= (b))
#define cfor(i,c) for(auto i = (c).begin() ; i!= (c).end(); i++)
#define el "\n"
#define ret return
#define F first
#define S second
#define YES cout<<"YES\n"
#define NO cout<<"NO\n"
#define all(v) (v).begin(),(v).end()
#define eps 0.00000001

/*##################################################################################*/


bool prime[10005] = {true};
vector < ll > pr;
void calculateprime()
{
    prime[0] = prime[1] = false;
    for(int i = 2 ; i*i <= 10005 ; i++)
    {
        if(prime[i] == true)
        {
            for(ll j = i*i ; j <= 10005 ; j += i )
            {
                prime[j] = false;
            }
        }
    }
}



void customrun(){
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

void fast(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}

ll powerwithmod(ll x, ll y, ll p = mod)
{
    ll res = 1;

    x = x % p;

    if (x == 0) return 0;

    while (y > 0)
    {
        if (y & 1)
            res = (res*x) % p;

        y = y>>1; // y = y/2
        x = (x*x) % p;
    }

    return res;
}

void solve();


int main() {
    clock_t begin = clock();
    srand(time(0));
    fast();

    customrun();

    ll t = 1;
    // cin>>t;
    // calculateprime();

    mfor(i,1,t+1,1)
    {
        // cout<<"Case #"<<i<<": ";

        solve();
    }
    clock_t end = clock();
    double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
    // cout<<"\ntime spent is "<<time_spent;
    return 0;
}

void solve(){
    ll v, e;
    cin>>v>>e;

    vector<vector< pair<ll,ll> > > g(v);

    for(int i = 0 ; i < e ; i++){
        ll a,b;
        cin>>a>>b;

        --a;
        --b;


        g[a].push_back({b, 1});
        g[b].push_back({a, -1});
    }

    ll s, d;
    cin>>s>>d;
    --s;--d;

    vector<pair<ll,ll> > dis(v, {INT_MAX, 10});
    vector<bool> used(v, false);
    priority_queue<pll, vector<pll>, greater<pll> > pq;

    pq.push({0,s});
    dis[s] = {0,0};

    // cout<<"hello";

    while(!pq.empty()){
        ll nxt = pq.top().second;
        ll dnxt = pq.top().first;
        pq.pop();

        if(dnxt != dis[nxt].first) continue;

        if(dis[nxt].first == INT_MAX) break;

        for(auto &i : g[nxt]){
            ll to = i.first;
            ll dir = i.second;

            if(dis[to].first > dis[nxt].first + ( dis[nxt].second + dir == 0 ) ){
                dis[to].first = dis[nxt].first + ( dis[nxt].second + dir == 0 );
                dis[to].second = dir;

                pq.push({dis[to].first, to});
            }
        }
    }

    // for(auto i : dis) cout<<i.first<<" "<<i.second<<endl;

    cout<< dis[d].first;
}