1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <string>
 5 #include <cstring>
 6 #include <cstdio>
 7 #include <math.h>
 8 #include <queue>
 9 #include <stack>
10 #include <map>
11 #include <cassert>
12 #include <set>
13 using namespace std;
14
15
16 const int N=323456;
17
18 struct Edge {
19     int to,next;
20     Edge() {}
21     Edge(int _to,int _next):to(_to),next(_next) {}
22 } edge[N<<2];
23 int idx=1,head[N];
24 inline void addedge(int u,int v) {
25     edge[++idx]=Edge(v,head[u]);
26     head[u]=idx;
27 }
28 bool vis[N];
29
30 void bfs(int s,int *dis) {
31     memset(vis,false,sizeof vis);
32     queue<int>que;
33     que.push(s);
34     vis[s]=true;
35     dis[s]=0;
36     while (!que.empty()) {
37         int u=que.front();
38         que.pop();
39         for (int k=head[u];k;k=edge[k].next) {
40             int v=edge[k].to;
41             if (vis[v]) continue;
42             dis[v]=dis[u]+1;
43             vis[v]=true;
44             que.push(v);
45         }
46     }
47 }
48 int dis[3][N];
49 int main () {
50     int n,m;
51     while (scanf("%d %d",&n,&m)==2) {
52         int s,a,b;
53         scanf("%d %d %d",&s,&a,&b);
54         idx=1;memset(head,0,sizeof head);
55         for (int i=1;i<=m;i++) {
56             int u,v;
57             scanf("%d %d",&u,&v);
58             addedge(u,v);
59             addedge(v,u);
60         }
61         bfs(s,dis[0]);
62         bfs(a,dis[1]);
63         bfs(b,dis[2]);
64         int da=dis[0][a];
65         int db=dis[0][b];
66         int ret=0;
67         for (int i=1;i<=n;i++) {
68             if (dis[0][i]+dis[1][i]==da&&dis[0][i]+dis[2][i]==db) {
69                 ret=max(ret,dis[0][i]);
70             }
71         }
72         cout<<ret<<endl;
73     }
74     return 0;
75 }