def find_two_sum(arr, target):
    """
    Finds the two (not necessarily distinct) indices of the first two integers
    in arr that sum to target, in sorted ascending order (or returns None if no
    such pair exists).
    """
    prev_map = {}  # Maps (target - arr[i]) -> i.
    for curr_idx, num in enumerate(arr):
        # Putting this block *before* the next block allows for the possibility
        # that prev_idx == curr_idx. If this isn't desired, then put it after.
        comp = target - num
        if comp not in prev_map:  # Don't overwrite the previous mapping.
            prev_map[comp] = curr_idx
        # Check if arr[curr_idx] matches some (target - arr[prev_idx]).
        if num in prev_map:
            prev_idx = prev_map[num]
            return prev_idx, curr_idx
    return None