#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  cin >> n;
  int count = 0;
  while (n != 0) {
    if (n % 10 == 4 || n % 10 == 7) {
      count += 1;
    }
    n /= 10;
  }
  if (count == 4 || count == 7) {
    cout << "YES"
         << "\n";
  } else {
    cout << "NO"
         << "\n";
  }
  return 0;
}
