#include<stdio.h>
int main() {
    long long n;
    if(scanf("%11d",&n) != 1) {
        printf("Invalid Input");
        return 0;
    }
    if (n <= 0) {
        printf("-1");
        return 0;
    }
    char result[100];
    int index = 0;
    while (n > 0) {
        n--;
        int rem = n % 26;
        result[index++] = 'A'+ rem;
        n /= 26;
    }
    for (int i = index - 1; i >= 0; i--) {
        printf("%c",result[i]);
    }
    return 0;
}