results=[] m,n=map(int,input().split()) #列数是n，行数是m for x in range(m): a=list(map(int,input().split())) results.append(a) tou_wei=sum(results[0])+sum(results[m-1]) res=0 for i in range(1,m-1): s=results[i][0]+results[i][n-1] res+=s zuizhong=tou_wei+res print(zuizhong)