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

#define int long long  

signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

 	int n, m;
 	cin >> n >> m;
	vector<int> col(n + 1);
	for (int i = 1; i <= n; i++) {
		char c;
		cin >> c;

		col[i] = c == 'o' ? 0 : 1;
	}

	vector cnt(n + 1, vector<int>(2));
	vector<pair<int, int>> e(m);
	for (int i = 0; i < m; i++) {
		int x, y;
		cin >> x >> y;
		e[i] = {x, y};

		if (col[x] != col[y]) {
			cnt[x][col[y]]++;
			cnt[y][col[x]]++;
		}
	}

	int ans = 0;
	for (auto [x, y] : e) {
		if (col[x] != col[y]) {
			ans += (cnt[x][col[y]] - 1) * (cnt[y][col[x]] - 1);
		}
	}

	cout << ans << "\n";

    return 0;
}