#include <stdio.h>

int main() {
    long long n;
    if (scanf("%lld", &n) != 1) {   // if input is not an integer
        printf("Invalid Input\n");
        return 0;
    }

    if (n < 0) {
        printf("-1\n");
        return 0;
    }
    if (n == 0) {   // Excel column starts at 1
        printf("Invalid Input\n");
        return 0;
    }

    char col[20];   // enough for n < 1e6
    int pos = 0;

    while (n > 0) {
        int rem = (n - 1) % 26;
        col[pos++] = 'A' + rem;
        n = (n - 1) / 26;