#include<bits/stdc++.h>

using namespace std;
using ll=long long;
#define rep2(i, a, n) for(int i = (a); i < (n); i++)
#define rep(i, n) rep2(i,0,n)

int main(){
  cin.tie(nullptr);ios_base::sync_with_stdio(false);
  int n;
  string s;
  cin>>n>>s;
  int cnt=0;
  rep(i,n){
    rep2(j,i+1,n){
      if(s[i]=='U'){
        if(s[j]=='M'){
          if(j*2-i>=0&&j*2-i<n){
            //cout<<s[i]<<" "<<s[j]<<" "<<s[j*2-1]<<endl;
            if(s[j*2-i]=='G')cnt++;
          }
        }
      }
    }
  }
  cout<<cnt<<endl;
}