#include <stdio.h>
#include <math.h>

int main() {

    long long length;
    scanf("%lld", &length);
    char sequence[length];
    fflush(stdin);
    getchar();
    for(int i=0; i<length; i++){
        sequence[i] = getchar();
    }
    int maxIterations = sqrt(length);
    long long result = 0, step, innerSquare;
    long long red, blue;
    for (int subsequence = 3; subsequence <= maxIterations; ++subsequence) {
        step = subsequence * subsequence;
        red = blue = 0;
        innerSquare = (subsequence-2)*(subsequence-2);
        for (int i = 0; i <= length - step; ++i) {
            if (i == 0) {
                for (int j = 0; j < step; ++j) {
                    if (sequence[j] == 'X')
                        blue++;
                    else
                        red++;
                }
            } else {
                if (sequence[i - 1] == 'X')
                    blue--;
                else
                    red--;

                if (sequence[step + i - 1] == 'X')
                    blue++;
                else
                    red++;
            }
            if (blue >= step - innerSquare && red >= innerSquare)
                result++;
        }
    }

    printf("%lld\n", result);

    return 0;
}