#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 2e5 + 10;
char c[N];
vector<int> vt[N];
vector<int> b[N];
ll dfs(int u, int fa, int ffa, char now, int height)
{
    if (height == 3)
    {
        // cout << u << " " << b[u].size() << endl;
        return b[u].size() - 1;
    }
    ll ans = 0;
    for (auto v : vt[u])
    {
        if (v == fa || v == ffa)
            continue;
        if (c[v] == now)
            continue;
        ans += dfs(v, u, fa, c[v], height + 1);
    }
    return ans;
}
int main()
{
    int n, m;
    while (scanf("%d%d", &n, &m) != EOF)
    {
        vector<int> bb;
        for (int i = 1; i <= n; i++)
        {
            b[i].clear();
            vt[i].clear();
            cin >> c[i];
            if (c[i] == 'b')
                bb.push_back(i);
        }
        for (int i = 1; i <= m; i++)
        {
            int u, v;
            scanf("%d%d", &u, &v);
            if (c[u] == 'b' && c[v] == 'o')
            {
                b[u].push_back(v);
                vt[u].push_back(v);
                vt[v].push_back(u);
            }
            else if (c[u] == 'o' && c[v] == 'b')
            {
                b[v].push_back(u);
                vt[u].push_back(v);
                vt[v].push_back(u);
            }
        }
        ll ans = 0;
        for (int i = 0; i < bb.size(); i++)
        {
            ans += dfs(bb[i], -1, -1, 'b', 1);
        }
        printf("%lld\n", ans);
    }
    return 0;
}