a.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;
	int maxn = 105;
	vector<int> g[maxn];

    for(int i=0; i<m; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }

    int start, end;
    cin >> start >> end;

    queue<int> q;
    q.push(start);
    int dist[maxn];
    for(int i=1; i<=n; i++) {
        dist[i]=-1;
    }
    dist[start] = 0;

    while(!q.empty()) {
        int v = q.front();
        q.pop();

        for(int to : g[v]) {
            if(dist[to] == -1) {
                dist[to] = dist[v]+1;
                q.push(to);
            }
        }
    }

    cout << dist[end];
}