theorem Th33:
  for a,b,c being odd Prime st c-b = 2 & b-a = 2 holds a = 3 & b = 5 & c = 7
  proof
    let a,b,c be odd Prime such that
A1: c-b = 2 & b-a = 2;
    3 divides a or 3 divides b or 3 divides c by A1,Th32;
    then a = 3 or b = 3 or c = 3 by INT_2:def 4;
    hence thesis by A1,INT_2:def 4;
  end;
