C++ :

#include <bits/stdc++.h>

using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n;
    string s;
    cin >> n >> s;
    int64_t ans = 0;
    for(int i = 0; i < n; i++) {
        int64_t lhs = 0;
        if(i > 0 && s[i-1] != s[i]) {
            lhs++;
            for(int k = i-2; k >= 0 && s[k] == s[i-1]; k--) lhs++;
        }
        int64_t rhs = 0;
        if(i+1 < n && s[i+1] != s[i]) {
            rhs++;
            for(int k = i+2; k < n && s[k] == s[i+1]; k++) rhs++;
        }
        ans += lhs * rhs + max(lhs-1, (int64_t)0) + max(rhs-1, (int64_t)0);
    }
    cout << ans << "\n";
    return 0;
}