#include <iostream>
#include <fstream>
using namespace std;
int n;

void citire()
{fstream f("ciur.in",ios::in);
f>>n;
f.close();
}

void ciur()
{fstream g("ciur.out",ios::out);
int i,j,x=0;
char v[2000002];
for(i=1;i<=n;i++)
    v[i]=0;
v[2]=1;
i=2;
while(i<=n)
{j=2;x++;
while(j*i<=n)
{v[i*j]=1;
j++;}
i++;
 while((v[i]==1)&&(i<=n))
        i++;
}

g<<x;
g.close();

}
int main()


{citire();
ciur();

}