var input = require('fs').readFileSync('/dev/stdin', 'utf8');

var N = +input

var alpha = 'abcdefghijklmnopqrstuvwxyz'.split('');

var name = [];
do {
    N = N - 1;
    name.unshift(alpha[N % 26])
    N = Math.floor(N / 26)
} while(N > 0)

console.log(name.join(''));