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

   function putere(x:longint):longint;
   begin
   k:=0;
   s:=1;
   while s<x do
   begin
   s:=s*5;
   k:=k+1;
   end;
   l:=1;
   d:=0;
   for i:=1 to k 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>200 then n:=(p*125 div 31) -200
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.