var n,p:longint;
    f:text;

procedure citire;
var f:text;
begin
     assign(f,'fact.in');
     reset(f);
     read(f,p);
     close(f);
end;

function cinci(m,x,putere:longint):longint;
begin
     if (p>=m)or(p>=m-putere+1) then cinci:=cinci(m+x,x*5,putere+1)
     else begin cinci:=m-x div 5; n:=n+x div 5 end
end;

begin
     citire;
     assign(f,'fact.out');
     rewrite(f);
     n:=0;
     if p=0 then write (f,'1')
     else begin while p>0 do
                      begin
                           p:=p-cinci(0,1,0);
                      end;
                write(f,n);
          end;
     close(f);
end.