!-----  Ex1_1: ３種類の平均値   -----
   PROGRAM Example_1_1
      REAL :: a, b, av1, av2, av3
      READ *, a, b
         av1 = (a + b)/2.0
         av2 = (a*b)**0.5
         av3 = 2.0/(1.0/a + 1.0/b)
      PRINT*, av1, av2, av3
   END