#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    int n, m; cin >> n >> m;
    string s; cin >> s;
    vector<vector<int>> vec(n + 1);
    vector<bool> vis(n + 1);
    for (int i = 1; i <= m; i++) {
        int u, v; cin >> u >> v;
        vec[u].push_back(v);
        vec[v].push_back(u);
    }
    s = ' ' + s;
    int ans = 0;
    char check[] = {0, 'b', 'o', 'b', 'o'};
    function<void(int, int)> dfs = [&] (int x, int now) {
        // cout << "x = " << x << '\n';
        // cout << "now = " << now << '\n';
        if (now == 4) {
            ans++;
            return;
        }
        for (int i = 0; i < vec[x].size(); i++) {
            int y = vec[x][i];
            if (vis[y]) continue;
            vis[y] = 1;
            if (check[now + 1] == s[y]) dfs(y, now + 1);
            vis[y] = 0;
        }
    };
    for (int i = 1; i <= n; i++) {
        if (s[i] == 'b') {
            vis[i] = 1;
            dfs(i, 1);
            vis[i] = 0;
        }
    }
    cout << ans << '\n';
    return 0;
}