def main(): # 读取矩阵的行数m和列数n m, n = map(int, input().split()) matrix = [] # 读取矩阵的每个元素 for _ in range(m): row = list(map(int, input().split())) matrix.append(row) # 初始化边缘元素之和为0 perimeter_sum = 0 # 遍历矩阵，累加边缘元素 for i in range(m): for j in range(n): # 如果是第一行或最后一行，或者第一列或最后一列 if i == 0 or i == m - 1 or j == 0 or j == n - 1: perimeter_sum += matrix[i][j] # 输出边缘元素之和 print(perimeter_sum) if __name__ == "__main__": main()