шифр вижинера

#include <iostream>
#include <string>
#include <cmath>
#include <thread>
#include <vector>

std::string alp = "abcdefghijklmnopqrstuvwxyz";
std::string message = "koh rhkbv woe tzp efscw soqzld yt jmub sigsdsyae";

void decipher(const std::string& key, int num) {
    std::string result = message;
    for (int i = 0, j = 0; i < message.length(); ++i, j %= key.length()) {
        if (result[i] == ' ')
            continue;
        result[i] = alp[(message[i] + (alp.length() - key[j++])) % alp.length()];
    }
    if (result.find(" you ") != std::string::npos)
        std::cout << key << " " << result << " " << num << '\n';
}

void func(int num) {
    for (int i = (num - 1) * std::pow(26, 5) / 12; i < num * std::pow(26, 5) / 12; ++i) {
        std::string key = "";
        for (int j = 0; j < 5; ++j)
            key += alp[i / static_cast<int>(std::pow(26, 5 - j - 1)) % 26];
        decipher(key, num);
    }
}

int main(int argc, char* argv[]) {
    std::vector<std::thread> ths;

    for (int i = 1; i <= 12; ++i)
        ths.push_back(std::thread(func, i));

    for (int i = 0; i < 12; ++i)
        ths[i].join();

    return 0;
}