if let n = Int(readLine() ?? "0"){
    var nums:[[Int]] = Array(repeating: Array(repeating: 0 , count: n), count: n)
    for i in 0..<n {
        if let input = readLine(), let numsLine = input.split(separator: " ").compactMap({Int($0)}) as? [Int], numsLine.count == i+1 {
            for j in 0...i {
                nums[i][j] = numsLine[j]
            }
        }
    }
    
    if n != 1 {
        for i in (0...(n-2)).reversed() {
            for j in 0...i {
                nums[i][j] += max(nums[i+1][j],nums[i+1][j+1])
            }
        }
    }

    print(nums[0][0])
}