#include<stdio.h>
int main(){
    long long n;
    scanf("%lld",&n);
    if(n < 0){
        printf("-1");
        return 0;
    }
    if(n == 0){
    printf("Invalid input");
    return 0;
    }
    char result[50];
    int index=0;
    while(n>0){
        n_;
        int rem = n % 26;
        result[index++] = 'A'+ rem;
        n = n/26;
    }
    for (int i = index - 1; i >= 0; i--){
        printf("%c", result[i]);
    }
    return 0;
}