row,col = input().split() row = int(row) col = int(col) a = [] for i in range(row): tmp = input().split() tmp = [int(x)for x in tmp] a.append(tmp) res=0 for i in range(row): for j in range(col): if i==0 or i==row-1: res=res+a[i][j] elif j==0 or j == col-1: res=res+a[i][j] print(res)