#include<iostream>
using namespace std;
int main()
{
int b; int i = 0;
long long a;
cin >> a;
{
while (a>0)
{
if (a % 10 == 4 || a % 10 == 7)
{
a = a / 10;
i++;
}
else
{
a = a / 10;
}
}
}
if (i == 4||i==7)
cout << "YES";
else
cout << "NO";
}
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