var  p,p2,c,n2,n,n3,x:longint  ;f,g:text;
begin
     assign(f,'fact.in'); reset(f);
     assign(g,'fact.out');rewrite(g);
     read(f,p);
     c:=1;
     n:=2000000000;
     n2:=n;    p2:=0;
     if p>0 then
     while p2<>p do begin
           if (p2>p) then
               n2:=(c+n2-1) div 2
           else if p2<>0 then begin
                c:=n2;
                n2:=n3;
                n2:=(c+n2-1) div 2;
           end;
           x:=5; p2:=0;
           while n2 div x>0 do begin
                 p2:=p2+n2 div x;
                 x:=x*5;
           end;
           if p2>p then n3:=n2
     end;
     writeln(g,n2);
     close(g);
end.