#include <stdio.h>

int main()
{
	char S[11];
	scanf("%s", S);

	unsigned m = 0;
	int i;
	for (i = 0; S[i]; i++) {
		unsigned n = 1 << (S[i]-'A');
		if (m & n) {
			puts("NO");
			return 0;
		}
		m |= n;
	}
	puts("YES");
	return 0;
}