Given two strings s and t, return the number of distinct subsequences of s which equals t. A subsequence of a string is obtained by deleting some characters without changing the order of the remaining characters. Please implement the following function:

``` def numDistinct(s: str, t: str) -> int: m, n = len(s), len(t) dp = [[0] * (n + 1) for _ in range(m + 1)] for i in range(m + 1): dp[i][0] = 1 for i in range(1, m + 1): for j in range(1, n + 1): dp[i][j] = dp[i - 1][j] if s[i - 1] == t[j - 1]: dp[i][j] += dp[i - 1][j - 1] return dp[m][n] ```