#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int my_sum(int y){ int ans=0; for(int i=2;i<=y;i++){ if(i==2){ ans+=1; continue; } for(int j=2;j<=i/2+1;j++){ if(i%j==0){ break; } if(j==i/2+1&&i%j!=0){ ans+=1; } } } return ans; } int main(){ int d; cin>>d; cout<<my_sum(d)<<endl; return 0; }