! 例題 5-5  最大公約数 ［無限ループ ］
PROGRAM ex5_5

  IMPLICIT NONE
  INTEGER :: m, n, mn, k

  PRINT *, 'Input two integers m, n ( > 0 ): '
  READ *, m, n
  mn = m * n

  IF ( m > 0 .AND. n > 0 ) THEN
    DO
      k = MOD( m, n )
      IF ( k == 0 ) EXIT
      m = n
      n = k
    END DO

    IF ( n > 1 ) THEN
      PRINT '( 1X, A, I10 )', '最大公約数 = ', n
    ELSE
      PRINT '( 1X, A )', '公約数なし'
    END IF

    n = mn / n
    PRINT '( 1X, A, I10 )', '最小公倍数 = ', n

  END IF

END PROGRAM ex5_5