var p,x,n:longint;
    i:byte;
    f,g:text;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
readln(f,p);
x:=p*5;n:=5;
{for i:=1 to 11 do
    begin
    n:=n*5;
    if x>=n then x:=x-5
            else break;
    end;}
for i:=1 to 11 do
    begin
    n:=n*5;
    if x div n>0 then x:=x-5*((x div n)-1);
    end;
write(g,x);
close(f);close(g);
end.