#include <iostream>

size_t square(size_t n) {
    return n * n;
}

size_t subseqCnt(const std::string& tiles) {
    size_t subseqCnt = 0u;
    const size_t tileCnt = tiles.size();

    for (size_t sideLen = 3u; square(sideLen) <= tileCnt; ++sideLen) {
        size_t xCnt = 0u;
        size_t i = 0u;
        const size_t squareTiles = square(sideLen);

        while (i < squareTiles) {
            if (tiles.at(i++) == 'X')
                ++xCnt;
        }

        bool isPatio = xCnt == 4 * (sideLen - 1) || xCnt == square(sideLen - 2);

        if (isPatio)
            ++subseqCnt;

        while (i < tileCnt) {
            char newTile = tiles.at(i);

            if (isPatio && newTile == tiles.at(i - squareTiles)) {
                ++subseqCnt;
                ++i;
                continue;
            }

            xCnt += (newTile == 'X') ? 1 : -1;
            isPatio = xCnt == 4 * (sideLen - 1) || xCnt == square(sideLen - 2);

            if (isPatio)
                ++subseqCnt;

            ++i;
        }
    }

    return subseqCnt;
}

int main() {
    size_t tileCnt;
    std::string tiles;

    std::cin >> tileCnt >> tiles;
    std::cout << subseqCnt(tiles) << std::endl;

    return 0;
}