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

