#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define fore(i,a) for(auto &i:a)

typedef pair <int, int> P;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
const int  INF = 2147483647;
const ll INFL = 9223372036854775807;
const ll mod = 1000000007;

VI a[100005];
string s;

ll ans = 0;

void dfs(int b, int c) {
	for (int i : a[b]) {
		if (c == 1 && s[i] == 'D')dfs(i, 2);
		else if (c == 2 && s[i] == 'C')dfs(i, 3);
		else if (c == 3 && s[i] == 'A')ans++;
	}
}


int main() {

	int n, m;
	cin >> n >> m >> s;

	REP(i, m) {
		int u, v;
		cin >> u >> v;
		u--, v--;
		a[u].push_back(v);
		a[v].push_back(u);
	}

	REP(i, n) {
		if (s[i] == 'P') dfs(i, 1);
	}

	cout << ans << endl;

	

	return 0;
	
}