#include <bits/stdc++.h>
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define mid ((x + y) / 2)
#define left (ind * 2)
#define right (ind * 2 + 1)
#define mp make_pair
#define timer ((double)clock() / CLOCKS_PER_SEC)
#define endl "\n"
#define spc " "
#define d1(x) cerr<<#x<<":"<<x<<endl
#define d2(x, y) cerr<<#x<<":"<<x<<" "<<#y<<":"<<y<<endl
#define d3(x, y, z) cerr<<#x<<":"<<x<<" "<<#y<<":"<<y<<" "<<#z<<":"<<z<<endl
#define fast_io() ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
using namespace std;
typedef long long int lli;
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
typedef pair<double, double> dd;
const int N = (int)(1e6 + 5);
const int LOG = (int)(20);
int n, m, cs1[N], cs2[N], s, d, a, b, ans;
vector<int> v[N];
void bfs1() {
queue<int> q;
q.push(s);
memset(cs1, -1, sizeof cs1);
cs1[s] = 0;
while(!q.empty()) {
int t = q.front();
q.pop();
for(auto i : v[t]) {
if(cs1[i] == -1) {
cs1[i] = cs1[t] + 1;
q.push(i);
}
}
}
}
void bfs2() {
queue<int> q;
q.push(d);
memset(cs2, -1, sizeof cs1);
cs2[d] = 0;
while(!q.empty()) {
int t = q.front();
q.pop();
for(auto i : v[t]) {
if(cs2[i] == -1) {
cs2[i] = cs2[t] + 1;
q.push(i);
}
}
}
}
int main() {
fast_io();
// freopen("inp.in", "r", stdin);
cin >> n >> m;
cin >> s >> d >> a >> b;
for(int i = 1; i <= m; i++) {
int aa, bb;
cin >> aa >> bb;
v[aa].pb(bb);
v[bb].pb(aa);
}
bfs1();
bfs2();
ans = min(cs2[a] - cs1[a], cs2[b] - cs1[b]);
ans = max(ans, 0);
cout << 0;
}
