#include <iostream>
using namespace std;

string a;
int w;

int main()
{
    cin >> a;

    if(a.size() == 1){ cout << "NO"; return 0;}

    for(int i = 0; i < a.size(); i++)  if(a[i] == '7' || a[i] == '4') w+=1;

    if(w == 0)           { cout <<  "NO"; return 0;}
    if(w == 4 || w == 7) { cout << "YES"; return 0;}

    cout << "NO";

}