dp to store the length of the longest subsequence ending with elements at indices i and j.(i, j) where i < j.(i, j), search for an index k such that arr[i] + arr[j] == arr[k] using binary search or a set.k exists, update dp[j, k] to be dp[i, j] + 1 or 3 if (i, j) is not in dp.0 if no Fibonacci-like subsequence is found.