sr=input().split()
m=int(sr[0])
n=int(sr[1])
a=[[0 for i in range(n)] for j in range(m)]
s=[[0 for i in range(n)] for j in range(m)]
for i in range(m):
    sr=input().split()
    for j in range(n):
        a[i][j]=int(sr[j])
for i in range(m):
    for j in range(n):
        if(i>0 and j>0):
            s[i][j]=a[i][j]+max(s[i-1][j],s[i][j-1])
        elif(i>0):
            s[i][0]=a[i][0]+s[i-1][0]
        elif(j>0):
            s[0][j]=a[0][j]+s[0][j-1]
        else:
            s[0][0]=a[0][0]
print(s[m-1][n-1])
/**************************************************************
	Problem: 1298
	User: admin
	Language: Python
	Result: Accepted
	Time:98 ms
	Memory:34480 kb
****************************************************************/