fs = require('fs');
input = fs.readFileSync('/dev/stdin','utf8');
N = parseInt(input,10);
A = 'abcdefghijklmnopqrstuvwxyz'.split('');
R = '';
while(N >= 1) {
  M = N % 26;
  R = A[M - 1] + R;
  N = (N - M) / 26;
}
console.log(R);
