#include <bits/stdc++.h>
using namespace std;
ifstream file("input.txt");
int main() {
  int ta = 0, tb = 0, tc = 0, v = 2;
  string str;
  cin >> str;
  for (int i = 0; i < str.size(); i++) {
    if (str[i] == 'a')
      ta++;
    else if (str[i] == 'b')
      tb++;
    else
      tc++;
  }
  for (int i = 0; i < str.size() - 1; i++)
    if (int(str[i]) > str[i + 1]) {
      v--;
      break;
    }
  if (tc != ta && tc != tb)
    v--;
  else if (ta == 0 || tb == 0 || tc == 0)
    v--;
  if (v == 2) {
    cout << "YES";
  } else
    cout << "NO";
}
