var f:text;
    j,k,i,n,p:longint;

function keres(a:longint):longint;
var s,b:longint;
begin
 s:=0;
 b:=1;
 while b<=a do
 begin
  b:=b*5;
  s:=s+a div b;
 end;
 keres:=s;
end;

begin
 assign(f,'fact.in');
 reset(f);
 readln(f,p);
 close(f);
 if p=0 then begin
  i:=1;
 end
 else begin
  i:=5;
  while keres(i)<p do inc(i,5);
 end;
 assign(f,'fact.out');
 rewrite(f);
 writeln(f,i);
 close(f);
end.