
theorem
  103 is prime
proof
  now
    103 = 2*51 + 1; hence not 2 divides 103 by NAT_4:9;
    103 = 3*34 + 1; hence not 3 divides 103 by NAT_4:9;
    103 = 5*20 + 3; hence not 5 divides 103 by NAT_4:9;
    103 = 7*14 + 5; hence not 7 divides 103 by NAT_4:9;
  end;
  then for n being Element of NAT st 1 < n & n*n <= 103 & n is prime
  holds not n divides 103 by XPRIMET1:8;
  hence thesis by NAT_4:14;
