var sum = [0]

ARGF.each {  |line|
    var x = line.words.map{.to_n}
    sum = [
            x.first + sum.first,
            1 ..^ x.end -> map{|i| x[i] + [sum[i-1, i]].max}...,
            x.last + sum.last,
          ]
}

say sum.max