"use strict";
    
const main = arg => {
    arg = arg.trim().split("\n");
    let N = parseInt(arg[0].split(" ")[0]);
    const alphabets = "abcdefghijklmnopqrstuvwxyz".split("");
    
    let answer = "";
    
    while(0 < N) {
        let m = N % 26;
        
        if(m === 0) m = 26;
        
        answer = alphabets[m-1] + answer;
        N = (N - m) / 26;
    }
    
    console.log(answer);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));