#include <iostream>
#include <math.h>
#include <vector>
#include <string>

#define MAX_SIDE 447
#define MIN_SIDE 3

#define BLUE 'X'
#define RED 'O'

using namespace std;
struct patio_layout {
    int side, inner, outer, sum;
    explicit patio_layout (int side_) : side(side_), outer((side_-1)*4), inner((side_-2)*(side_-2)), sum(inner + outer) {}
};

int main() {

    vector<patio_layout> patio_sizes;
    for (int i = MIN_SIDE; i <= MAX_SIDE; ++i) {
        patio_sizes.emplace_back(i);
    }

    int n;
    cin >> n;
    vector<int> prefix_blue;
    vector<int> prefix_red;

    prefix_blue.push_back(0);
    prefix_red.push_back(0);

    string s;
    getline(cin, s);

    for (int i = 0; i < n; ++i) {
        char c;
        cin >> c;
        prefix_blue.push_back(prefix_blue[i]);
        prefix_red.push_back(prefix_red[i]);
        if (c == BLUE) {
            prefix_blue[i+1]++;
        } else {
            prefix_red[i+1]++;
        }
    }

    long long cnt = 0;

    for (int i = 0; i <= n; ++i) {
        for (auto & size : patio_sizes) {
            if (i + size.sum > n)
                break;
            int blue = prefix_blue[i+size.sum] - prefix_blue[i];
            int red = prefix_red[i+size.sum] - prefix_red[i];
            if ((blue == size.inner && red == size.outer)
            ||  (red == size.inner && blue == size.outer)) {
                cnt++;
            }
        }
    }

    std::cout << cnt << std::endl;
    return 0;
}