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diff --git a/linux/apps/advent2017/1a.mu b/linux/apps/advent2017/1a.mu
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+# Advent of code 2017, problem 1a
+#   https://adventofcode.com/2017/day/1
+#
+# Mu solution by Sumeet Agarwal and Kartik Agaram
+#   https://archive.org/details/2021-06-02-akkartik-sumeet
+#
+# To build on Linux:
+#   $ git clone https://github.com/akkartik/mu
+#   $ cd mu/linux
+#   $ ./translate apps/advent2017/1a.mu            # emits a.elf
+# To run on Linux:
+#   Download https://adventofcode.com/2017/day/1/input
+#   $ ./a.elf < input
+# Type in the number returned at https://adventofcode.com/2017/day/1
+
+fn main -> _/ebx: int {
+  var input_stream: (stream byte 0x8000)
+  var input_stream_addr/esi: (addr stream byte) <- address input_stream
+
+  var sum/edi: int <- copy 0
+  read-line-from-real-keyboard input_stream_addr
+
+  var temp/eax: int <- read_digit input_stream_addr
+  var first_digit/ebx: int <- copy temp
+  var this_digit/edx: int <- copy temp
+
+  {
+    var done?/eax: boolean <- stream-empty? input_stream_addr
+    compare done?, 1
+    break-if-=
+
+    var next_digit/eax: int <- read_digit input_stream_addr
+    # hacky newline check
+    compare next_digit, 0
+    break-if-<
+
+    {
+      compare this_digit, next_digit
+      break-if-!=
+      sum <- add this_digit
+    }
+
+    this_digit <- copy next_digit
+    
+    loop
+  }
+
+  # the last iteration will need to compare the last number to the first
+  {
+    compare this_digit, first_digit
+    break-if-!=
+    sum <- add this_digit
+  }
+
+  print-int32-decimal 0, sum
+  
+  return 0/ok
+}
+
+fn read_digit input_stream_addr: (addr stream byte) -> _/eax: int {
+  var next_digit/eax: byte <- read-byte input_stream_addr
+  next_digit <- subtract 0x30
+  var next_digit/eax: int <- copy next_digit
+  return next_digit
+}