I found an interesting problem on https://www.codechef.com/problems/MAXSC:
You are given N integer sequences A1, A2, ..., AN. Each of these sequences contains N elements. You should pick N elements, one from each sequence; let's denote the element picked from sequence Ai by Ei. For each i (2 ≤ i ≤ N), Ei should be strictly greater than Ei-1.
Compute the maximum possible value of E1 + E2 + ... + EN. If it's impossible to pick the elements E1, E2, ..., EN, print -1 instead.

-----Input-----

- The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.
- The first line of each test case contains a single integer N.
- N lines follow. For each valid i, the i-th of these lines contains N space-separated integers Ai1, Ai2, ..., AiN denoting the elements of the sequence Ai.

-----Output-----
For each test case, print a single line containing one integer — the maximum sum of picked elements.

-----Constraints-----
- 1 ≤ T ≤ 10
- 1 ≤ N ≤ 700
- 1 ≤ sum of N in all test-cases ≤ 3700
- 1 ≤ Aij ≤ 109 for each valid i, j

-----Subtasks-----
Subtask #1 (18 points): 1 ≤ Aij ≤ N for each valid i, j
Subtask #2 (82 points): original constraints

-----Example-----
Input:

1
3
1 2 3
4 5 6
7 8 9

Output:

18

-----Explanation-----
Example case 1: To maximise the score, pick 3 from the first row, 6 from the second row and 9 from the third row. The resulting sum is E1+E2+E3 = 3+6+9 = 18.

I tried it in Python, but could not do it. Can you solve it?
# cook your dish here
t=int(input())
for cases in range(t):
 n=int(input())
 lis=[]
 for i in range(n):
  lis1=sorted(list(map(int,input().split())))
  lis.append(lis1)
 summ=lis[-1][-1]
 maxx=summ
 c=1
 for i in range(n-2,-1,-1):
  for j in range(n-1,-1,-1):
   if lis[i][j]<maxx:
    maxx=lis[i][j]
    c+=1
    summ+=lis[i][j]
    break
 if c==n:
  print(summ)
 else:
  print(-1)
 print()