1
#include <bits/stdc++.h>
2
#define ll long long
3
 
4
using namespace std;
5
 
6
int main() {
7
    int n, m;
8
    cin >> n >> m;
9
    vector<int> g[n + 1];
10
    for (int i = 0; i < m; ++i) {
11
        int x, y;
12
        cin >> x >> y;
13
        g[x].push_back(y);
14
        g[y].push_back(x);
15
    }
16
    
17
    int s, f;
18
    cin >> s >> f;
19
    
20
    vector<bool> used(n + 1, false);
21
    vector<int> d(n + 1, 0);
22
    queue<int> q;
23
    
24
    used[s] = true;
25
    d[s] = 0;
26
	q.push(s);
27
	
28
	while (!q.empty()) {
29
	    int v = q.front();
30
	    q.pop();
31
	    for (int to: g[v]) {
32
	        if (!used[to]) {
33
	            used[to] = true;
34
	            d[to] = d[v] + 1;
35
	            q.push(to);
36
	        }
37
	    }
38
	}
39
	
40
	if (!used[f]) {
41
	    cout << -1;
42
	} else {
43
	    cout << d[f];
44
	}
45
	return 0;
46
}
47