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

var N = +input

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

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

name.unshift(alpha[N % 26 - 1]);

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



