#include <stdio.h>

int main() {
  int alp[26]={}, i, cnt=0;
  char s[11];
  scanf("%s", s);

  for (i=0; s[i]!='\0'; i++) {
    alp[s[i]-'A']++;
    if (alp[s[i]-'A']>1) {
      printf("NO\n");
      return 0;
    }
  }

  printf("YES\n");
  return 0;
}