var f,g:text;
    x,k,l,p,j,s,n,b,d,q:int64;
    i:integer;

   function putere(x:int64):int64;
   begin
   l:=1;
   d:=0;
   for i:=1 to 25 do
   begin
   l:=l*5;
   d:=d+(x div l);
   end;
   putere:=d;
   end;

begin
assign(f,'fact.in');
assign(g,'fact.out');
reset(f);
rewrite(g);
 read(f,p);
if p>300 then n:=(p*125 div 31) -1000
else
 n:=0;

while putere(n)<p do
n:=n+1;

if putere(n)=p then write(g,n)
else write(g,'-1');
close(f);
close(g);
end.