#include<stdio.h>
#include<stdlib.h>
#include<string.h>
 void numberToExcelTitle(int n){
     if(n<=0){
         return;
     }
     char title[100];
     int index = 0;
     while(n>0){
         n--;
         title[index++] = (n%26) + 'A';
         n/=26;
     }
     title[index] = '\0';
     for(int i= index - 1;i>=0;i--){
         putchar(title[i]);
     }
     putchar("\n";)
 }
 int main()
 {
     int n;
     if(scanf("%d", &n) <=0){
         printf("Invalid input");
         return 1;
     }
     if(n<=0){
         printf("-1");
         return 1;
     }
     numbeToExcelTitle(n);
     return 0;
 }