function Main(input) {
    input = input.trim();
    const n = parseInt(input, 10);
    const alpha = ['z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y'];

    let ans = '';
    let m = n;
    while(m>=26){
        ans = alpha[m%26] + ans;
        m = parseInt(m/26, 10);
    }
    ans = alpha[m] + ans;
    console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));