var  n,p:longint; f,g:text;
function fac(n:longint):longint;
var k,s:longint;
begin
s:=0;k:=1;
while k<=n do begin
k:=k*5;
s:=s+(n div k);
end;
fac:=s;
end;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
readln(f,p);
n:=0;
repeat
n:=n+5;
until fac(n)>=p;
if fac(n)=p then
write(g,n) else write(g,-1);
close(f);
close(g);
end.