2021 day2/python: add solution

2021/data/day2.expected

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+1714680
+1963088820

2021/day2/day2.py

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+#!/usr/bin/env python
+
+import sys
+
+if __name__ == '__main__':
+    x = 0
+    y = 0
+    z = 0
+    for line in sys.stdin.readlines():
+        dir, amount = line.split()
+        amount = int(amount)
+        if dir == 'forward':
+            x += amount
+            z += y * amount
+        elif dir == 'down':
+            y += amount
+        elif dir == 'up':
+            y -= amount
+    print(x*y)
+    print(x*z)