var f,g:text;
    n,k,nr,p:longint;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
read(f,p);
if p<>0 then begin
n:=p*5;
k:=125;
if n>k then nr:=n div k-1;
p:=p-nr;
n:=5*p;
end;
if p<>0 then write(g,n)
   else write(g,'1');
close(f);
close(g);
end.