Codeforces 110A Nearly Lucky Number

A. Nearly Lucky Number

Solution in c++

#include<bits/stdc++.h>

#include<string.h>

#include<stdio.h>

#include<math.h>

#include<algorithm>

using namespace std;

int main()

{  

int n,i,key,start,ln,end,mid,ass;

string arr;

cin>>arr;

ln=arr.length();

//cout<<ln;

end=0;

for(i=0;i<ln;i++){

if(arr[i]=='4' || arr[i]=='7')

end++;

}

if(end==4 || end==7){

cout<<"YES"<<endl;

}

else {

cout<<"NO"<<endl;

}

}