program fact;
uses crt;
var p,n,aux:longint;
    put:byte;
    f,g:text;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
readln(f,p);
n:=0;
while p>0 do begin
    inc(n,5);
    put:=0;
    aux:=n;
    while aux mod 5=0 do begin
                       inc(put);
                       aux:=aux div 5;
                       end;
    p:=p-put;
    end;
if p<0 then writeln(g,-1)
       else writeln(g,n);
close(f);
close(g);
end.