#include <stdio.h>

typedef long long ll;

int calc(ll n, ll t, int c)
{
	if( n <= t*27-1 ) return c;
	return calc( n, t*27, c+1);
}

int main(void)
{
	int i, j, c;
	ll n;
	char s[10];
	scanf("%lld", &n);

	if( n <= 25 ) {
		printf("%c\n", 'A'+n);
		return 0;
	}

	c = calc( n, 26, 2 );
	s[c] = '\0';

	for( i = 0; i < c-1; i++) {
		ll t = 26, u;
		for( j = 1; t*27-1 < n; j++) t *= 27;
		u = n/t;
		n -= t*u;
		if( u ) {
			s[i] = 'A'+(char)u-1;
		} else {
			s[i] = 'A'+u;
		}
	}
	s[c-1] = 'A'+n;

	for( i = 0; s[i] != '\0'; i++){
		printf("%c", s[i]);
	}
	printf("\n");

	return 0;
}