new file mode 100644
--- /dev/null
+++ b/2017/day12/problem
@@ -0,0 +1,78 @@
+--- Day 12: Digital Plumber ---
+
+Walking along the memory banks of the stream, you find a small village
+that is experiencing a little confusion: some programs can't
+communicate with each other.
+
+Programs in this village communicate using a fixed system of pipes.
+Messages are passed between programs using these pipes, but most
+programs aren't connected to each other directly. Instead, programs
+pass messages between each other until the message reaches the
+intended recipient.
+
+For some reason, though, some of these messages aren't ever reaching
+their intended recipient, and the programs suspect that some pipes are
+missing. They would like you to investigate.
+
+You walk through the village and record the ID of each program and the
+IDs with which it can communicate directly (your puzzle input). Each
+program has one or more programs with which it can communicate, and
+these pipes are bidirectional; if 8 says it can communicate with 11,
+then 11 will say it can communicate with 8.
+
+You need to figure out how many programs are in the group that
+contains program ID 0.
+
+For example, suppose you go door-to-door like a travelling salesman
+and record the following list:
+
+0 <-> 2
+1 <-> 1
+2 <-> 0, 3, 4
+3 <-> 2, 4
+4 <-> 2, 3, 6
+5 <-> 6
+6 <-> 4, 5
+
+In this example, the following programs are in the group that contains
+program ID 0:
+
+    Program 0 by definition.
+
+    Program 2, directly connected to program 0.
+
+    Program 3 via program 2.
+
+    Program 4 via program 2.
+
+    Program 5 via programs 6, then 4, then 2.
+
+    Program 6 via programs 4, then 2.
+
+
+Therefore, a total of 6 programs are in this group; all but program 1,
+which has a pipe that connects it to itself.
+
+How many programs are in the group that contains program ID 0?
+
+Your puzzle answer was 141.
+
+--- Part Two ---
+
+There are more programs than just the ones in the group containing
+program ID 0. The rest of them have no way of reaching that group, and
+still might have no way of reaching each other.
+
+A group is a collection of programs that can all communicate via pipes
+either directly or indirectly. The programs you identified just a
+moment ago are all part of the same group. Now, they would like you to
+determine the total number of groups.
+
+In the example above, there were 2 groups: one consisting of programs
+0,2,3,4,5,6, and the other consisting solely of program 1.
+
+How many groups are there in total?
+
+Your puzzle answer was 171.
+
+Both parts of this puzzle are complete! They provide two gold stars: **