#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n;
  while (cin >> n) {
    bool flag = false;
    int sum = 0;
    while (n) {
      if (n % 10 == 4 || n % 10 == 7)
        n /= 10, sum++;
      else
        n /= 10;
    }
    if ((sum == 4 || sum == 7))
      cout << "YES" << endl;
    else
      cout << "NO" << endl;
  }
}
