#include <bits/stdc++.h>
using namespace std;
int main() {
  int i = 0, a = 0, b = 0, c = 0;
  string s;
  cin >> s;
  for (; i < s.length(); i++) {
    if (s[i] == 'a')
      a++;
    else
      break;
  }
  for (; i < s.length(); i++) {
    if (s[i] == 'b')
      b++;
    else
      break;
  }
  for (; i < s.length(); i++) {
    if (s[i] == 'c')
      c++;
    else
      break;
  }
  if (i != s.length() || (c != a && c != b) || a == 0 || b == 0)
    cout << "NO" << endl;
  else
    cout << "YES" << endl;
  return 0;
}
