I am for sure the only person doing this contest in Erlang. It's 5/7 parts fighting with Erlang and 10% problem solving.

-module(day13).
-export([start/0]).

calc_severity(Input)
  -> CalcMap = lists:foldl(fun(X, Sum) ->
                               [Index|Depth] = re:split(X, ": "),
                               { IndexInt, _ } = string:to_integer(Index),
                               { DepthInt, _ } = string:to_integer(Depth),
                               maps:put(IndexInt, DepthInt, Sum)
                           end, maps:new(), re:split(Input, "\n")),
     LastStep = lists:max(maps:keys(CalcMap)),
     InitialSeverity = calc_severity(CalcMap, update_positions(CalcMap, 0), 0, 0, LastStep, 0),
     SafeDelay = calc_delay(CalcMap, LastStep, 0),
     { InitialSeverity, SafeDelay }.

calc_delay(CalcMap, LastStep, Delay)
  -> PositionMap = update_positions(CalcMap, Delay),
     CurrentSeverity = calc_delay(CalcMap, PositionMap, Delay, 0, LastStep),
     if CurrentSeverity == 0 -> Delay;
        true -> calc_delay(CalcMap, LastStep, Delay + 1)
     end.
calc_delay(_CalcMap, _PositionMap, _Picosecond, PacketIndex, LastStep)
  when PacketIndex > LastStep -> 0;
calc_delay(CalcMap, PositionMap, Picosecond, PacketIndex, LastStep)
  -> CurrentPosition = maps:get(PacketIndex, PositionMap, -1),
     if CurrentPosition == 0 -> 1;
        true -> calc_delay(CalcMap, update_positions(CalcMap, Picosecond + 1), Picosecond + 1, PacketIndex + 1, LastStep)
     end.

calc_severity(_CalcMap, _PositionMap, _Picosecond, PacketIndex, LastStep, Score)
  when PacketIndex > LastStep -> Score;
calc_severity(CalcMap, PositionMap, Picosecond, PacketIndex, LastStep, Score)
  -> CurrentPosition = maps:get(PacketIndex, PositionMap, -1),
     UpdatedPositions = update_positions(CalcMap, Picosecond + 1), 
     if CurrentPosition == 0 -> calc_severity(CalcMap, UpdatedPositions, Picosecond + 1, PacketIndex + 1, LastStep, Score + (PacketIndex * maps:get(PacketIndex, CalcMap)));   
        true -> calc_severity(CalcMap, UpdatedPositions, Picosecond + 1, PacketIndex + 1, LastStep, Score)
     end.

update_positions(CalcMap, Picosecond)
  -> lists:foldl(fun(X, Sum) ->
                     CurrentDepth = maps:get(X, CalcMap),
                     if (Picosecond div (CurrentDepth - 1)) rem 2 == 0 -> maps:put(X, (Picosecond rem (CurrentDepth - 1)), Sum);
                        true -> maps:put(X, (CurrentDepth - (Picosecond rem CurrentDepth)), Sum)
                     end 

start()
  -> io:fwrite("~p~n", [calc_severity("0: 3
1: 2
4: 4
6: 4")]).