diff --git a/day1/input b/day1/input
new file mode 100644
index 0000000..7205e6f
--- /dev/null
+++ b/day1/input
@@ -0,0 +1,200 @@
+1977
+1802
+1856
+1309
+2003
+1854
+1898
+1862
+1857
+542
+1616
+1599
+1628
+1511
+1848
+1623
+1959
+1693
+1444
+1211
+1551
+1399
+1855
+1538
+1869
+1664
+1719
+1241
+1875
+1733
+1547
+1813
+1531
+1773
+624
+1336
+1897
+1179
+1258
+1205
+1727
+1364
+1957
+540
+1970
+1273
+1621
+1964
+1723
+1699
+1847
+1249
+1254
+1644
+1449
+1794
+1797
+1713
+1534
+1202
+1951
+1598
+1926
+1865
+1294
+1893
+1641
+1325
+1432
+1960
+413
+1517
+1724
+1715
+1458
+1775
+1317
+1694
+1484
+1840
+1999
+1811
+1578
+1658
+1906
+1481
+1313
+1997
+1339
+1592
+1971
+1453
+1706
+1884
+1956
+1384
+1579
+1689
+1726
+1217
+1796
+1536
+1213
+1867
+1304
+2010
+1503
+1665
+1361
+814
+2007
+1430
+1625
+1958
+860
+1799
+1942
+1876
+1772
+1198
+1221
+1814
+1826
+1667
+1334
+1504
+1420
+1164
+1414
+1934
+1823
+1507
+1195
+21
+1752
+1472
+1196
+1558
+1322
+1927
+1556
+1922
+277
+1828
+1883
+1280
+1947
+1231
+1915
+1235
+1961
+1494
+1324
+2009
+1367
+1545
+1736
+1575
+1214
+1704
+1833
+1663
+1474
+1894
+1754
+1564
+1321
+1119
+1975
+1987
+1873
+1834
+1686
+1574
+1505
+1656
+1688
+1896
+1982
+1554
+1990
+1902
+1859
+1293
+1739
+1282
+1889
+1981
+1283
+1687
+1220
+1443
+1409
+1252
+1506
+1742
+1319
+1882
+951
+1849
diff --git a/day1/main.hs b/day1/main.hs
new file mode 100755
index 0000000..c9ef9fe
--- /dev/null
+++ b/day1/main.hs
@@ -0,0 +1,37 @@
+#! /usr/bin/env -S"ANSWER=42" nix-shell
+#! nix-shell -p ghcid
+#! nix-shell -p "haskellPackages.ghcWithPackages (p: with p; [shower])"
+#! nix-shell -i "ghcid -c 'ghci -Wall' -T main"
+
+{-# LANGUAGE OverloadedStrings #-}
+
+-- [...] find the two entries that sum to 2020 and then multiply those two
+-- numbers together.
+
+testData :: [Int]
+testData = [ 1721 , 979 , 366 , 299 , 675 , 1456 ]
+
+realData :: [Int]
+realData = [ 1977 , 1802 , 1856 , 1309 , 2003 , 1854 , 1898 , 1862 , 1857 , 542 , 1616 , 1599 , 1628 , 1511 , 1848 , 1623 , 1959 , 1693 , 1444 , 1211 , 1551 , 1399 , 1855 , 1538 , 1869 , 1664 , 1719 , 1241 , 1875 , 1733 , 1547 , 1813 , 1531 , 1773 , 624 , 1336 , 1897 , 1179 , 1258 , 1205 , 1727 , 1364 , 1957 , 540 , 1970 , 1273 , 1621 , 1964 , 1723 , 1699 , 1847 , 1249 , 1254 , 1644 , 1449 , 1794 , 1797 , 1713 , 1534 , 1202 , 1951 , 1598 , 1926 , 1865 , 1294 , 1893 , 1641 , 1325 , 1432 , 1960 , 413 , 1517 , 1724 , 1715 , 1458 , 1775 , 1317 , 1694 , 1484 , 1840 , 1999 , 1811 , 1578 , 1658 , 1906 , 1481 , 1313 , 1997 , 1339 , 1592 , 1971 , 1453 , 1706 , 1884 , 1956 , 1384 , 1579 , 1689 , 1726 , 1217 , 1796 , 1536 , 1213 , 1867 , 1304 , 2010 , 1503 , 1665 , 1361 , 814 , 2007 , 1430 , 1625 , 1958 , 860 , 1799 , 1942 , 1876 , 1772 , 1198 , 1221 , 1814 , 1826 , 1667 , 1334 , 1504 , 1420 , 1164 , 1414 , 1934 , 1823 , 1507 , 1195 , 21 , 1752 , 1472 , 1196 , 1558 , 1322 , 1927 , 1556 , 1922 , 277 , 1828 , 1883 , 1280 , 1947 , 1231 , 1915 , 1235 , 1961 , 1494 , 1324 , 2009 , 1367 , 1545 , 1736 , 1575 , 1214 , 1704 , 1833 , 1663 , 1474 , 1894 , 1754 , 1564 , 1321 , 1119 , 1975 , 1987 , 1873 , 1834 , 1686 , 1574 , 1505 , 1656 , 1688 , 1896 , 1982 , 1554 , 1990 , 1902 , 1859 , 1293 , 1739 , 1282 , 1889 , 1981 , 1283 , 1687 , 1220 , 1443 , 1409 , 1252 , 1506 , 1742 , 1319 , 1882 , 951 , 1849 ]
+
+solve1 :: [Int] -> Maybe Int
+solve1 l = lookup 2020 $ do
+  x <- l
+  y <- l
+  pure (x+y,x*y)
+
+solve2 :: [Int] -> Maybe Int
+solve2 l = lookup 2020 $ do
+  x <- l
+  y <- l
+  z <- l
+  pure (x+y+z,x*y*z)
+
+main :: IO ()
+main = do
+  putStrLn "Day 1 - Part 1"
+  print $ solve1 testData
+  print $ solve1 realData
+  putStrLn "Day 1 - Part 2"
+  print $ solve2 testData
+  print $ solve2 realData