var a,b,m,n,i,j:longint;

function f(n:longint):longint;
var i,j:longint;
 begin
  i:=0;
  while n>0 do
   begin
    j:=(n div 5);
    i:=i+j;
    n:=j;
   end;
  f:=i;
 end;

procedure fact(m,n:longint);
var i,j:longint;
 begin
  i:=(m+n) div 2;
  j:=f(i);
  if M<n then
   begin
    if j>=a then fact(m,i-1) else
     if j<a then fact(i+1,n);
   end else   b:=m;
 end;

begin
assign(input,'fact.in');
reset(input);
read(a);
close(input);
m:=1;
n:=2009000000;
fact(m,n);
assign(output,'fact.out');
rewrite(output);
if f(b)=a then write(b) else if f(b+1)=a then write(b+1)
else if f(b+2)=a then write(b+2) else if f(b-1)=a then write(b-1)
else write(-1);

close(output);
end.