#include <bits/stdc++.h>
#define ll long long
#define rep(i,s,t) for(int i=(s);i<=(t);i++)
#define rev_rep(i,s,t) for(int i=(s);i>=(t);i--)
using namespace std;
ll ci(){ ll x; scanf("%lld", &x); return x; }

enum{N=200023};

int cnt[2][N];
char s[N];

signed main(){
	int n, m;
	while( scanf("%d%d", &n,&m)!=EOF ){
		scanf("%s", s+1);
		vector<pair<int,int> > e;
		rep(i,1,n) cnt[0][i] = cnt[1][i] = 0;
		rep(i,1,m){
			int x = ci(), y = ci();
			cnt[s[y]=='o'][x]++;
			cnt[s[x]=='o'][y]++;
			if( s[x]!=s[y] ){
				if( s[x]=='b' ) swap(x,y);
				e.push_back({x,y});
			}
		}
	//rep(i,1,n) printf("%lld ", cnt[0][i]); puts("");
	//rep(i,1,n) printf("%lld ", cnt[1][i]); puts("");
		ll ans = 0;
		for(auto[x,y]:e){
		//printf("line %d: xy %d %d\n", __LINE__, x,y);
			ans += (cnt[0][x]-1) * (cnt[1][y]-1);
		}
		printf("%lld\n", ans);
	}
	return 0;
}