#include <bits/stdc++.h>
#define dbg(x) cerr << #x << ':'<< (x) << endl;
#define ALL(x) x.begin(),x.end()
using namespace std;
using ll = long long;
using ld = long double;

int main()
{
    int n,m;
    cin >> n >> m;

    vector<int> s(n);
    for (int i = 0; i < n; i++) cin >> s[i];

    vector<vector<vector<int>>> g(2,vector<vector<int>>(n));
    for (int i = 0; i < m; i++) {
        int u,v;
        cin >> u >> v;
        --u;--v;
        g[s[v]][u].emplace_back(v);
        g[s[u]][v].emplace_back(u);
    }

    // infinityの判定
    vector<bool> used(n);
    queue<int> que;
    vector<vector<int>> cnt(2,vector<int>(n));
    for (int i = 0; i < n; i++) {
        if (g[0][i].empty() || g[1][i].empty()) {
            used[i] = true;
            que.push(i);
        }
        cnt[0][i] = g[0][i].size();
        cnt[1][i] = g[1][i].size();
    }

    while (!que.empty()) {
        int x = que.front();
        que.pop();

        for (int y : g[0][x]) {
            --cnt[s[x]][y];
            if (!used[y] && cnt[s[x]][y] == 0) {
                used[y] = true;
                que.push(y);
            }
        }
        for (int y : g[1][x]) {
            --cnt[s[x]][y];
            if (!used[y] && cnt[s[x]][y] == 0) {
                used[y] = true;
                que.push(y);
            }
        }
    }
    bool infinity_flag = false;
    for (int i = 0; i < n; i++) {
        if (!used[i]) {
            infinity_flag = true;
        }
    }

    if (infinity_flag) {
       cout << "infinity" << endl;
       return 0;
    }

    int ans = INT_MAX;
    for (int i = 0; i < 4; i++) {
        vector<vector<int>> dis(2,vector<int>(n,0));
        queue<pair<int,int>> q;
        for (int j = 0; j < n; j++) {
            if (s[j] == (i&1)) {
                dis[i>>1][j] = 1;
                q.push({i>>1,j});
            }
        }

        bool inf_flag = false;
        while (!q.empty()) {
            auto [num,x] = q.front();
            q.pop();
            // cerr << "s:" << num << ' ' << x << endl;

            for (int y : g[1-num][x]) {
                if (dis[s[x]][y] != 0) {
                    // if (dis[s[x]][y] != dis[num][x]+1) inf_flag = true;
                    continue;
                }
                // cerr << "t:" << s[x] << ' ' << y << endl;
                dis[s[x]][y] = dis[num][x]+1;
                q.push({s[x],y});
            }
            if (inf_flag) break;
        }

        int tmp = 0;
        for (int j = 0; j < 2; j++) for (int k = 0; k < n; k++) tmp = max(tmp,dis[j][k]);
        if (!inf_flag) ans = min(ans, tmp+1);
    }
    
    // if (ans == INT_MAX) cout << "infinity" << endl;
    // else cout << ans << endl;
    cout << ans << endl;

    return 0;
}