#include <stdio.h>
#include <string.h>

int main(void)
{
	char s[11];
	char a[] = "ABCDEFGHIJKLMNOPQRWTUVWXYZ";
	int  n[26] = {0};
	int judge = 0;
	int i, j;

	scanf("%s", s);
	
	for (i = 0; i < strlen(s); i++) {
		for (j = 0; j < 26; j++) {
			if (s[i] == a[j])
				n[j]++;
		}
	}

	for (i = 0; i < 26; i++) {
		if (n[i] >= 2) {
			judge++;
			break;
		}
	}

	printf("%s\n", judge ? "NO" : "YES");

	return 0;
}