program ciur_eratostene;   
var f,g:text;   
    n:longint;   
    i,j,nr:longint;   
    ciur:array[1..2000000]of byte;
begin  
     assign(f,'ciur.in');   
     assign(g,'ciur.out');   
     reset(f);   
     rewrite(g);   
     read(f,n);   
     nr:=0;   
     for i:=1 to n do  
         ciur[i]:=1;   
     for i:=2 to(n div 2)do  
         for j:=2 to(n div i)do  
             ciur[i*j]:=0;   
     for i:=3 to n do  
         if (ciur[i]=1)then  
            inc(nr);   
     write(g,nr+1);   
     close(f);   
     close(g);   
end.