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

//#define int long long
#define f(i,a,b) for(int i = (a); i < (b); ++i)

signed main() {
    ios_base::sync_with_stdio(0);
    int n;
    cin >> n;
    string s;
    cin >> s;
    vector<int> ss(n+1);
    for (int i=0; i < n; ++i) ss[i+1] = ss[i] + (s[i] == 'X');

    int ans = 0;

    for (int i=0; i <= n; ++i) {
        for (int l=3; l*l <= i; ++l) {
            if (ss[i]-ss[i-l*l] == (l-2)*(l-2) || ss[i]-ss[i-l*l] == 4*(l-1)) ans++;
        }
    }

    cout << ans << endl;

    return 0;
}