diff --git a/2019/day4.py b/2019/day4.py
new file mode 100644
index 0000000..4bd7d73
--- /dev/null
+++ b/2019/day4.py
@@ -0,0 +1,32 @@
+def main():
+    with open("day4.txt", "rt") as input_file:
+        first_line = input_file.readlines()[0]
+    lower_bound, upper_bound = tuple(first_line.strip().split("-"))
+    solve(int(lower_bound), int(upper_bound))
+
+def solve(lower_bound, upper_bound):
+    validity_map = map(lambda v: int(is_valid(v)), range(lower_bound, upper_bound))
+    print("Num valids:", sum(validity_map))
+
+def is_valid(value):
+    return has_adjacents(value) and is_increasing(value)
+
+def has_adjacents(value):
+    digits = [get_digit(value, index) for index in range(6)]
+    for i in range(6 - 1):
+        if digits[i] == digits[i + 1]:
+            return True
+    return False
+
+def is_increasing(value):
+    digits = [get_digit(value, index) for index in range(6)]
+    for i in range(6 - 1):
+        if digits[i + 1] < digits[i]:
+            return False
+    return True
+
+def get_digit(value, index):
+    return int(str(value)[index])
+
+if __name__ == "__main__":
+    main()