var li,lf,w,p,a:longint;

procedure cautare_bin(li,lf:longint);
var i:int64;
begin

a:=((li+lf-1) div 2);
i:=5;
w:=0;
while trunc(a/i)>0 do
      begin
      w:=w+trunc(a/i);
      i:=i*5;
      end;
end;

procedure cautare;
var gasit:boolean;
begin
li:=1;
lf:=100000000;
gasit:=false;
while li<=lf do
      begin
      cautare_bin(li,lf);
      if w=p then
         begin
         gasit:=true;
         break
         end
         else if w<p then
                 begin
                 li:=a-1;
//                 cautare_bin(li,lf)
                 end
              else begin
                   lf:=a-1;
  //                 cautare_bin(li,a-1);
                   end;
      end;
if not gasit then
   a:=-1;
end;

procedure scriere;
begin
assign(output,'fact.out');
rewrite(output);
write(a);
close(output);
end;

procedure citire;
begin
assign(input,'fact.in');
reset(input);
read(p);
close(input);
end;

begin
citire;
cautare;
scriere;
end.