#include<cstdio>
void print(long long x){
  if(x==0)return;
  if(x%26==0)print((x/26)-1),putchar('z');
  else print(x/26),putchar('a'+(x%26)-1);
}
int main(){
  long long x;scanf("%lld",&x);
  print(x),puts("");
}