110A. Nearly Lucky Number.cpp

//============================================================================
//problem link:http://codeforces.com/problemset/problem/110/A
// Name        : 110A - Nearly Lucky Number.cpp
// Author      : mohand sakr
// Version     :
// Copyright   : use it under your responsibility
// Description : Hello World in C++, Ansi-style
//status:accepted
//============================================================================

#include <iostream>
#include<string>
#include<algorithm>
using namespace std;

int main() {

string s;
cin>>s;
int counter=0;
int len=s.length();
 int seven=count(s.begin(),s.end(),'4');
 int four=count(s.begin(),s.end(),'7');
 if((four+seven==4||four+seven==7))
	 cout<<"YES";
 else
 cout<<"NO";


	return 0;
}