import system'collections;
import extensions;

const int maxNumber = 100000;

Hailstone(int n,Map<int,int> lengths)
{
    if (n == 1)
    {
        ^ 1
    };

    while (true)
    {
        if (lengths.containsKey(n))
        {
            ^ lengths[n]
        }
        else
        {
            if (n.isEven())
            {
                lengths[n] := 1 + Hailstone(n/2, lengths)
            }
            else
            {
                lengths[n] := 1 + Hailstone(3*n + 1, lengths)
            }
        }
    }
}

public program()
{
    int longestChain := 0;
    int longestNumber := 0;
    auto recursiveLengths := new Map<int,int>(4096,4096);

    for(int i := 1; i < maxNumber; i+=1)
    {
        var chainLength := Hailstone(i, recursiveLengths);
        if (longestChain < chainLength)
        {
               longestChain := chainLength;
               longestNumber := i
        }
    };

    console.printFormatted("max below {0}: {1} ({2} steps)", maxNumber, longestNumber, longestChain)
}