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