'use strict';

function Main(input) {
    // N
    const N = input.trim().split('\n')[0];
    let bigN = BigInt(N);

    let bigArr = []
    while (bigN !== 0n) {
        const mod = bigN % 26n;
        if (mod === 0n) {
            bigArr.push(26n);
            bigN = bigN / 26n - 1n
        } else {
            bigArr.push(mod);
            bigN = bigN / 26n;
        }
    }
    let numArr = bigArr.map(v => Number(v));

    const alphabet = [
        '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', 'z'
        ];
    
    const result = numArr.map(v => alphabet[v - 1]).reverse().join('');

    console.log(result);

    return;
}
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));