编辑代码

program sum_1
    implicit none
    integer :: i
    real :: a, b, c, sum

    a = 2
    b = 1
    sum = a / b

    do i = 2, 20
        c = a + b
        a = b
        b = c
        sum = sum + a / b
    end do

    print *,sum
end program sum_1