var formats = [
    {|a,b,c|
        Hash(
            func   => {|d,e,f,g| ((d.$a(e)).$b(f)).$c(g) },
            format => "((%d #{a} %d) #{b} %d) #{c} %d"
        )
    },
    {|a,b,c|
        Hash(
            func   => {|d,e,f,g| (d.$a((e.$b(f)))).$c(g) },
            format => "(%d #{a} (%d #{b} %d)) #{c} %d",
        )
    },
    {|a,b,c|
        Hash(
            func   => {|d,e,f,g| (d.$a(e)).$b(f.$c(g)) },
            format => "(%d #{a} %d) #{b} (%d #{c} %d)",
        )
    },
    {|a,b,c|
        Hash(
            func   => {|d,e,f,g| (d.$a(e)).$b(f.$c(g)) },
            format => "(%d #{a} %d) #{b} (%d #{c} %d)",
        )
    },
    {|a,b,c|
        Hash(
            func   => {|d,e,f,g| d.$a(e.$b(f.$c(g))) },
            format => "%d #{a} (%d #{b} (%d #{c} %d))",
        )
    },
];

var op = %w( + - * / )
var blocks = op.map { |a| op.map { |b| op.map { |c| formats.map { |format|
    format(a,b,c)
}}}}.flat

loop {
    var input = Sys.scanln("Enter four integers or 'q' to exit: ");
    input == 'q' && break;

    if (input !~ /^\h*[1-9]\h+[1-9]\h+[1-9]\h+[1-9]\h*$/) {
        say "Invalid input!"
        next
    }

    var n = input.split.map{.to_n}
    var numbers = n.permutations

    blocks.each { |block|
        numbers.each { |n|
            if (block{:func}.call(n...) == 24) {
                say (block{:format} % (n...))
            }
        }
    }
}