1

cpp'

1. include <bits/stdc++.h>

using namespace std;

int jisuan(long long n) { for(long long i=2;i*i<=n;++i) if(n%i==0) return false;

   return true;
   

}

int main() { long long n,sum=0; cin>>n;

   for(long long i=2;i<=n;++i)
       if(jisuan(i)) ++sum;

cout<<sum; return 0; }