#include <iostream>
#include <string>

int main() {
    int n;
    std::string s;
    std::cin >> n >> s;
    int ans=0;
    for (int i=1;i<=n;i++) {
        if (s[i-1]=='U') {
            for (int j=i+1;j<=(n-i)/2+i;j++) {
                ans=((s[j-1]=='M')&&(s[2*j-i-1]=='G'))?ans+1:ans;
            }
        }
    }
    std::cout << ans << std::endl;
}