!-----  Ex5_5: 最大公約数を求める   -----
      INTEGER :: m, n, k
      PRINT*, 'Input two integers m, n (>0):'
      READ*, 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*, '最大公約数＝', n
         ELSE
            PRINT*,"公約数なし"
         END IF
      END IF
      END