/**
  @file 805.cpp
  @title  No.805 UMG - yukicoder
  @url https://yukicoder.me/problems/no/805
**/

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

typedef long long LL;
#define ALL(obj) (obj).begin(), (obj).end()
#define REP(i, N) for (int i = 0; i < (N); ++i)

int main() {
  int N;
  cin >> N;
  string S;
  cin >> S;

  vector<int> m;
  vector<int> dp_U(N + 1, 0);
  vector<int> dp_G(N + 1, 0);
  REP(i, N) {
    if (S.substr(i, 1) == "M") {
      m.push_back(i);
    }

    if (S.substr(i, 1) == "U") {
      dp_U[i + 1] = dp_U[i] + 1;
    } else {
      dp_U[i + 1] = dp_U[i];
    }

    if (S.substr(i, 1) == "G") {
      dp_G[i + 1] = dp_G[i] + 1;
    } else {
      dp_G[i + 1] = dp_G[i];
    }
  }

  int M = (int)m.size();

  int ans = 0;
  if (M != 0) {
    REP(i, M) {
      int numU = dp_U[m[i]] - dp_U[0];
      int numG = dp_G[N] - dp_G[m[i]];
      if (numU <= numG) {
        for (int j = 0; j < m[i]; j++) {
          // cout << "j\t" << j << " S[j]:\t" << S[j] << "\n";
          // cout << "m[i]+(m[i]-j)\t" << m[i] + (m[i] - j) << " S[]:\t" << S[j] << "\n";
          if (S[j] == 'U' && S[m[i]+(m[i]-j)] == 'G') {
            ans++;
          }
        }
      } else {
        for (int j = m[i] + 1; j < N; j++) {
          // cout << "j\t" << j << " S[j]:\t" << S[j] << "\n";
          // cout << "m[i]-(j-m[i])\t" << m[i] - (j - m[i]) << " S[]:\t" << S[m[i] - (j - m[i])] << "\n";
          if (S[j] == 'G' && S[m[i] - (j - m[i])] == 'U') {
            ans++;
          }
        }
      }
    }
  }

  cout << ans << endl;
  return 0;
}