var a,b,stop,c,e,n,p:longint;
function f(n:longint):longint;
var fact:longint;
begin
fact:=1;
e:=0;
while n div fact<>0 do
begin
fact:=fact*5;
if n div fact=0 then
break;
e:=e+n div fact;
end;
f:=e;
end;
begin
assign (input,'fact.in');
reset (input);
read (input,p);
close (input);
if p=0 then
begin
assign (output,'fact.out');
rewrite (output);
write (output,1);
close (output);
halt;
end
else
if p<=4 then
begin
assign (output,'fact.out');
rewrite (output);
write (output,p*5);
close (output);
halt;
end;
a:=0; b:=p*5; stop:=0;
while a<=b do
begin
c:=(a+b-5) div 2;
if f(c)<p then
a:=c+1
else
if f(c)>p then
b:=c-1
else
begin
stop:=p; a:=b+1;
end;
end;
assign (output,'fact.out');
rewrite (output);
if stop<>0 then
write (output,c)
else
write (output,-1);
close (output);
end.