a,b= map(int,input().split()) arr =[[0]*a]*b sums=0 for i in range(a): arr[i] = [int(j) for j in input().split()] if i ==0 or i==b-1: sums= sum(arr[i])+sums elif i>0 and i<b-1: sums=arr[i][0]+arr[i][b-1]+sums print(sums)