'use strict';

const inputs = require('fs').readFileSync('/dev/stdin', 'utf8').split('\n');
const foo = (str) => str.split(' ').map(v => parseInt(v, 10));

const number = foo(inputs[0])[0];

const table = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
const result = [];

solve(number);

console.log(result.reverse().join(''));

function solve(value) {
  if (value > 26) {
    result.push(table[(value % 26) - 1]);
    solve(Math.floor(value / 26));
  } else {
    result.push(table[value - 1]);
  }
}