#include <iostream> #include <cstdio> using namespace std; int a(int l){ int o=l,p=1,k=0; for(k=2;k<=o/2;k++){ if(o%k==0) p=0;} return p; } int main(){ int n,b,m=0,i; cin>>n; for (i=2;i<=n;i++) m+=a(i); cout<<m; return 0; }