666用字符串哪里错了

#include <bits/stdc++.h>
using namespace std;
int main()
{
     //freopen(".in","r",stdin);
    //freopen(".out","w",stdout);
    long long k,z=0;
    string s;
    cin>>s>>k;
    for(int i=0;i<s.size();i++){
    	if(s[i]==3) z++;
	}
   if(z=k) cout<<"YES"<<endl;
   else cout<<"NO"<<endl;

   return 0;
}