tzh神牛的程序（欠抽。。。哈哈）

program t274;

var

n,b,c:longint;

t:int64;

begin

t:=1;

read(n);

for b:=1 to n do

begin

t:=t*b;

while (t mod 10 =0) do t:=t div 10;

if t>100000000000 then t:=t mod 10000000000;

end;

c:=t mod 10;

write(c);

end.