#include <bits/stdc++.h>
char s[10005];
int main() {
  int len, i;
  int a, b, c, t;
  while (scanf("%s", s) != EOF) {
    a = 0;
    b = 0;
    c = 0;
    len = strlen(s);
    for (i = 0; i < len; i++) {
      if (s[i] == 'a')
        a++;
      else if (s[i] == 'b')
        b++;
      else
        c++;
    }
    if (a < b) {
      t = a;
      a = b;
      b = t;
    }
    if (a < c) {
      t = a;
      a = c;
      c = t;
    }
    if (b < c) {
      t = b;
      b = c;
      c = t;
    }
    if (a - c >= 2)
      printf("NO\n");
    else
      printf("YES\n");
  }
  return 0;
}
