Var i,n :integer;
Begin
Read(n);
Count:=0;
For i:=50 to n do
If i mod 3 = 0 then inc(count);
Write(count);
End.
Var i,n :integer;
Begin
Read(n);
Count:=0;
For i:=50 to n do
If i mod 3 = 0 then inc(count);
Write(count);
End.