program das;
var n,i,j:longint;
f,g:text;
s:word;
begin
assign (f,'fact.in');
reset (f);
read (f,n);
assign (g,'fact.out');
rewrite (g);
i:=0;
s:=0;
if (n<0) or (n>99999999) then write (g,'-1')
else begin
while s<>n do begin
i:=i+5;
j:=i;
while j mod 5=0 do begin s:=s+1;
                         j:=j div 5;
                         end;
end;
end;

write (g,i);
close (g);
end.