#include <iostream>
#include <memory>
#include <string>
#include <algorithm>
#include <math.h>

int main(){
    size_t length;
    std::string input;


    std::cin >> length >> input;

    size_t result = 0;

    for(size_t start = 0; start < input.size(); ++start){
        size_t xCounter = 0, oCounter = 0;

        for(size_t actual = start; actual < input.size(); ++actual){
            if(input[actual] == 'X'){
                xCounter++;
            } else {
                oCounter++;
            }

            if( (size_t) sqrt(oCounter) * 4 + 4 == xCounter && oCounter != 0){
                result++;
            }
            if( (size_t) sqrt(xCounter) * 4 + 4 == oCounter && xCounter != 0){
                result++;
            }
        }
    }

    std::cout << result << std::endl;

    return 0;
}