#include <bits/stdc++.h>
using namespace std;
int main() {
  string S;
  cin >> S;
  int n = S.size();
  int num[3] = {0};
  for (int i = 0; i < n; i++) {
    if (S[i] == 'a')
      num[0]++;
    else if (S[i] == 'b')
      num[1]++;
    else
      num[2]++;
  }
  sort(num, num + 3);
  string ans = "YES";
  if (num[2] > num[1] && num[1] > num[0]) ans = "NO";
  cout << ans << endl;
}
