diff --git a/day01/part1.nim b/day01/part1.nim
index 6829881..7274b20 100644
--- a/day01/part1.nim
+++ b/day01/part1.nim
@@ -1,3 +1,20 @@
+# Copyright 2021 Christian Ulrich
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# usage: ./part1 < input
+
 import strutils
 
 proc countIncreases(): uint =
diff --git a/day01/part2.nim b/day01/part2.nim
index 2727faa..05189d0 100644
--- a/day01/part2.nim
+++ b/day01/part2.nim
@@ -1,3 +1,20 @@
+# Copyright 2021 Christian Ulrich
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# usage: ./part2 < input
+
 import algorithm
 import math
 import strutils