program jiji_ya_four_la_mate;
var d,j,i,t,n:longint;
    s,s1:word;
    f,g:text;
begin
 assign(f,'cifra.in');
 reset(f);
 assign(g,'cifra.out');
 rewrite(g);
 read(f,n);
 read(f,t);
 readln(n);
 s1:=1;
 d:=0;
 for i:=1 to t do begin
  s:=i mod 10;
  for j:=1 to i do begin
   s1:=s1*s;
   s1:=s1 mod 10;
  end;
  d:=d+s1;
  d:=d mod 10;
 end;
 write(g,d);
 close(f);
 close(g);
end.