#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;
using u128 = unsigned __int128;

constexpr int inf = 1E9;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int n, m;
    std::cin >> n >> m;
    
    std::vector<int> a(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    
    std::vector<std::vector<int>> adj(n);
    std::vector<std::array<int, 2>> deg(n);
    for (int i = 0; i < m; i++) {
        int u, v;
        std::cin >> u >> v;
        u--;
        v--;
        adj[u].push_back(v);
        adj[v].push_back(u);
        deg[u][a[v]]++;
        deg[v][a[u]]++;
    }
    
    std::vector<std::array<int, 2>> dp(n, {inf, inf});
    std::queue<std::array<int, 2>> q;
    
    for (int i = 0; i < n; i++) {
        for (int t = 0; t < 2; t++) {
            if (deg[i][t] == 0) {
                dp[i][t] = 1;
                q.push({i, t});
            }
        }
    }
    while (!q.empty()) {
        auto [x, t] = q.front();
        q.pop();
        
        for (auto y : adj[x]) {
            if (a[y] == t) {
                continue;
            }
            if (--deg[y][a[x]] == 0) {
                dp[y][a[x]] = dp[x][t] + 1;
                q.push({y, a[x]});
            }
        }
    }
    
    int mx[2][2] {};
    for (int i = 0; i < n; i++) {
        for (int t = 0; t < 2; t++) {
            mx[a[i]][t] = std::max(mx[a[i]][t], dp[i][t]);
        }
    }
    
    int ans = inf;
    for (int x = 0; x < 2; x++) {
        for (int y = 0; y < 2; y++) {
            ans = std::min(ans, mx[x][y] + 1);
        }
    }
    if (ans == inf) {
        std::cout << "infinity\n";
        return 0;
    }
    
    std::cout << ans << "\n";
    
    return 0;
}