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

#define all(x) begin(x), end(x)

int fun(string& s, char one, char two, int N) {
    auto left = s.begin();
    auto right = s.begin();
    int answer = 0;
    int X = 0;
    int O = 0;
    for (int i = 1; i*i < N; ++i) {
        while (right < s.end() || left < s.end()) {
            if (X < i*i || O < 4 * (i + 1)) {
                if (right == s.end()) break;
                if (right[0] == one) X++; else O++;
                right++;
            } else if (X > i*i || O > 4 * (i + 1)) {
                if (left[0] == one) X--; else O--;
                left++;
            } else {
                answer++;
                if (left[0] == one) X--; else O--;
                left++;
            }
        }
    }
    return answer;
}

int main() {
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);

    int N;
    cin >> N;
    string s;
    cin >> s;
    assert(s.size() == N);



    cout << fun(s, 'O', 'X', N) << endl;


	return 0;
			
}