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

#define all(x) begin(x), end(x)
#ifdef CKISEKI
#define safe cerr << __PRETTY_FUNCTION__ << " line " << __LINE__ << " safe\n"
#define debug(a...) debug_(#a, a)
#define orange(a...) orange_(#a, a)
void debug_(auto s, auto ...a) {
  cerr << "\e[1;32m(" << s << ") = (";
  int f = 0;
  (..., (cerr << (f++ ? ", " : "") << a));
  cerr << ")\e[0m\n";
}
#include <experimental/iterator>
void orange_(auto s, auto L, auto R) {
  cerr << "\e[1;33m[ " << s << " ] = [ ";
  using namespace experimental;
  copy(L, R, make_ostream_joiner(cerr, ", "));
  cerr << " ]\e[0m\n";
}
#else
#define safe ((void)0)
#define debug(...) safe
#define orange(...) safe
#endif

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, m;
  while (cin >> n >> m) {
    string s;
    cin >> s;
    vector<pair<int, int>> e(m);
    for (auto &[u, v] : e) {
      cin >> u >> v;
      --u, --v;
    }

    for (auto &si : s) {
      if (si == 'b')
        si = '0';
      else si = '1';
    }

    vector<array<int, 2>> c(n);
    for (auto [u, v] : e) {
      c[u][s[v] - '0']++;
      c[v][s[u] - '0']++;
    }

    int64_t ans = 0;

    for (auto [u, v] : e) {
      if (s[u] == s[v])
        continue;
      if (s[u] == '0') {
        ans += int64_t(c[u][1] - 1) * (c[v][0] - 1);
      } else if (s[u] == '1') {
        ans += int64_t(c[u][0] - 1) * (c[v][1] - 1);
      }
    }

    cout << ans << '\n';
  }
  return 0;
}

/*
bobo
obob
*/