function Main(input) {
  input = input.replace(/\n/g, ' ');
  input = input.split(" ");
  var A = Number(input[0]);
  var P = ["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"]
  var ans = "";
  var num = [];
  var l = 0;
  while(true){
    num[l] = A%26 - 1;
    if(num[l] == -1)num[l]=25;
    A=(A-num[l]-1)/26;
    if(A == 0){break;}
    l++;
  }
  for(var i=num.length-1;i>=0;i--){
    ans+=P[Number(num[i])];
  }
  console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));