#include <stdio.h>

long long int n;
int ans[9];

int main(void) {
	scanf("%lld", &n);
	int c = 0;
	long long int d = 1;
	while(0 <= n) {
		ans[c] = (n / d) % 26; c++;
		d *= 26;
		n -= d;
	}
	c--;
	int i;
	for(i = c; 0 <= i; i--) {
		printf("%c", 'A' + ans[i]);
	}
	printf("\n");
	
	return 0;
}