def sum_of_edges(matrix): total_sum = 0 # 矩阵的行数和列数 m, n = matrix[0], matrix[1] # 遍历第一行 for i in range(n): total_sum += matrix[2][i] # 遍历最后一行 for i in range(n): total_sum += matrix[m-1][i] # 遍历第一列 for i in range(2, m): total_sum += matrix[i][0] # 遍历最后一列 for i in range(2, m): total_sum += matrix[i][n-1] return total_sum # 读取输入 m, n = map(int, input().split()) matrix = [] for _ in range(m): matrix.append(list(map(int, input().split()))) # 计算边缘元素之和 result = sum_of_edges([matrix, m, n]) print(result)