if __name__=="__main__":
    n=int(input())

    res=[]

    for x in range(0,n):
        temp = [int(x) for x in input().split()]
        res.append(temp)

    m = len(res[-1])
    dp = [[-0x3f3f3f3f for x in range(0,m+1)] for x in range(0,n+1)]

    dp[1][1]=res[0][0]

    for i in range(2,n+1):
        for j in range(1,m+1):
            if i>=j:
                dp[i][j] = max(dp[i-1][j],dp[i-1][j-1]) + res[i-1][j-1]


    print(max(dp[-1]))