#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>
#include <cstring>
#include <queue>
using namespace std;
const int maxn=2e5+5;
vector < int > ms[maxn];
int dist[2][maxn];
bool bio[2][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]);
}
}
}
}
void siri(int x, int y, int z){
bio[y][z][x]=1;
for(int i=0; i<(int)ms[x].size(); i++){
if(!bio[y][z][ms[x][i]] && dist[y][ms[x][i]]==dist[y][x]-1){
siri(ms[x][i], y, z);
}
}
}
int main(){
memset(dist, -1, sizeof(dist));
int n, m;
scanf("%d%d", &n, &m);
int a, b, c, d;
scanf("%d%d%d%d", &a, &b, &c, &d);
a--; b--; c--; d--;
int x, y;
for(int i=0; i<m; i++){
scanf("%d%d", &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]){
printf("-1\n");
}
else{
if(dist[0][c]-dist[1][c]==dist[0][d]-dist[1][d]){
siri(c, 0, 0);
siri(d, 0, 1);
siri(c, 1, 0);
siri(d, 1, 1);
int mini[2]={(int)1e9, (int)1e9};
int cvor[2];
int val;
for(int j=0; j<2; j++){
for(int i=0; i<n; i++){
if(bio[j][0][i] && bio[j][1][i]){
val=dist[j][c]-dist[j][i];
if(val<mini[j]){
mini[j]=val;
cvor[j]=i;
}
}
}
}
int raz=dist[1][c]-dist[0][c];
if(cvor[0]==cvor[1]){
printf("%d\n", raz);
}
else{
if(mini[0]<=mini[1]){
printf("%d\n", raz);
}
else{
printf("%d\n", raz-1);
}
}
}
else{
printf("%d\n", min(dist[1][c]-dist[0][c], dist[1][d]-dist[0][d]));
}
}
return 0;
}
