program nested_harmonic_sum
  implicit none
  integer :: i, j
  real(8) :: sum1, sum2, sum3, sum4
 
  ! Method 1: Double loop using DO
  sum1 = 0.0d0
  do i = 1, 100
     do j = 1, i
        sum1 = sum1 + 1.0d0 / dble(j)
     end do
  end do
  print *, 'sum1 =', sum1
 
  ! Method 2: Using WHILE-like structure with DO
  sum2 = 0.0d0
  i = 1
  do while (i < 100)
     j = 1
     do while (j < i)
        sum2 = sum2 + 1.0d0 / dble(j)
        j = j + 1
     end do
     i = i + 1
  end do
  print *, 'sum2 =', sum2
 
  ! Method 3: Nested FOR-like loops with inner sum
  sum3 = 0.0d0
  do i = 1, 99
     sum4 = 0.0d0
     do j = 1, i - 1
        sum4 = sum4 + 1.0d0 / dble(j)
     end do
     sum3 = sum3 + sum4
  end do
  print *, 'sum3 =', sum3
 
end program nested_harmonic_sum

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