#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <cstring>
#include <queue>
#include <cassert>
using namespace std;
const int maxn=2e5+5;
vector < int > ms[maxn];
int dist[2][maxn];
void bfs(int x, int ind){
queue < int > q;
q.push(x);
dist[ind][x]=0;
while(!q.empty()){
x=q.front();
q.pop();
for(int i=0; i<(int)ms[x].size(); i++){
if(dist[ind][ms[x][i]]==-1){
dist[ind][ms[x][i]]=dist[ind][x]+1;
q.push(ms[x][i]);
}
}
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
for(int i=0; i<2; i++){
memset(dist[i], -1, sizeof(dist[i]));
}
int n, m;
cin >> n >> m;
int a, b, c, d;
cin >> a >> b >> c >> d;
a--; b--; c--; d--;
assert(a!=b && a!=c && a!=d);
int x, y;
for(int i=0; i<m; i++){
cin >> x >> y;
x--; y--;
ms[x].push_back(y);
ms[y].push_back(x);
}
bfs(a, 0);
bfs(b, 1);
if(dist[0][c]>dist[1][c] || dist[0][d]>dist[1][d]){
cout << -1 << '\n';
}
/* else if(dist[0][c]==dist[1][c] || dist[0][d]==dist[1][d]){
cout << 0 << '\n';
}*/
else{
// assert(0);
cout << min(dist[1][c]-dist[0][c], dist[1][d]-dist[0][d]) << '\n';
}
return 0;
}
