input: Write a python function to determine the length of the smallest string that contains both str1 and str2 as subsequences.
  assert super_seq("AGGTAB", "GXTXAYB", 6, 7) == 9
  assert super_seq("feek", "eke", 4, 3) == 5
  assert super_seq("PARRT", "RTA", 5, 3) == 6
output: def super_seq(str1, str2, m, n):
      dp = [[0] * (n + 1) for _ in range(m + 1)]
      for i in range(m + 1):
          for j in range(n + 1):
              if i == 0:
                  dp[i][j] = j
              elif j == 0:
                  dp[i][j] = i
              elif str1[i - 1] == str2[j - 1]:
                  dp[i][j] = dp[i - 1][j - 1] + 1
              else:
                  dp[i][j] = 1 + min(dp[i - 1][j], dp[i][j - 1])
      return dp[m][n]