#include <iostream>
#include <string>
#include <algorithm>

std::string beolvas(std::istream &be = std::cin) {
    int n;
    be >> n;

    std::string gy;
    be >> gy;

    return gy;
}

int legtobb_gyumolcs(const std::string &gy) {
    const int n = static_cast<int>(gy.size());

    int a = 0;
    int k = static_cast<int>(std::count(gy.begin(), gy.end(), 'K'));
    for (int i = 0; i < n && a < k; i++) {
        a += gy[i] != 'K';
        k -= gy[i] == 'K';
    }

    return a << 1;
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);

    const auto gy = beolvas();
    std::cout << legtobb_gyumolcs(gy) << '\n';

    return 0;
}