#include<stdio.h>
int main(){
    long long n;
    char result[20];
    int index = 0;
    scanf("%11d", &n);
    if (n < 0){
        printf("-1");
        return 0;
    }
    if(n == 0){
        printf("Invalid Input");
        return 0;
    }
    while (n > 0){
        long long rem = (n - 1) % 26;
        result[index++] = 'A' + rem;
        n = (n - 1) / 26;
    }
    result[index] ='\0';
    for(int i = index - 1; i >= 0; i--){
        printf("%c", result[i]);
    }
    return 0;
}