def sum_of_diagonals(matrix, n): main_diagonal_sum = 0 secondary_diagonal_sum = 0 for i in range(n): main_diagonal_sum += matrix[i][i] secondary_diagonal_sum += matrix[i][n-1-i] return main_diagonal_sum + secondary_diagonal_sum # 输入矩阵的大小 n = int(input()) # 初始化矩阵，这里假设用户会按照题目要求输入矩阵的元素 matrix = [] for _ in range(n): row = list(map(int, input().split())) matrix.append(row) # 计算对角线之和 result = sum_of_diagonals(matrix, n) # 输出结果 print(result)