#include <stdio.h>

int main(void) {
    char S[11];
    int i, j;
    
    scanf("%s", S);
    for (i = 0; S[i] != 0; i++) {
    	for (j = i+1; S[j] != 0; j++) {
    		if (S[i] == S[j]) {
    			printf("NO");
    			return 0;
    		}
    	}
    }
    printf("YES");
}