#include<iostream> #include<cmath> using namespace std; bool isPrime(int num) { if (num<2) { return false; } for (int i=2;i<=sqrt(num);i++) { if (num%i== 0) { return false; } } return true; } int countPrimes(int n) { int count=0; for (int i=2;i<=n;i++) { if (isPrime(i)) { count++; } } return count; } int main() { int n; cin>>n; int primeCount=countPrimes(n); cout<<primeCount<<endl; return 0; }