#include <algorithm>
#include <iostream>
#include <map>
#include <vector>
#include <cstdio>

using namespace std;

int main()
{
	long long n; cin >>n;
	short c=0;
	while(n) {
		if( n%10==4 || n%10==7) c++;
		n /= 10;
	}
	
	puts( (c==4||c==7)?"YES":"NO" );

}