diff --git a/d20/part1.py b/d20/part1.py
new file mode 100644
index 0000000..4b4455a
--- /dev/null
+++ b/d20/part1.py
@@ -0,0 +1,49 @@
+from __future__ import annotations
+import sys
+from dataclasses import dataclass
+
+@dataclass
+class E:
+    v: int
+    p: E
+    n: E
+
+V0 = None
+p = None
+L = []
+for l in sys.stdin.read().splitlines():
+    e = E(int(l),p,None)
+    L.append(e)
+    if l == "0":
+        V0 = e
+    if p is not None:
+        p.n = e
+    p = e
+L[-1].n = L[0]
+L[0].p = L[-1]
+
+def swap(l,m):
+    k = l.p
+    n = m.n
+    k.n = m
+    n.p = l
+    l.n = n
+    m.p = k
+    l.p = m
+    m.n = l
+
+for l in L:
+    if l.v > 0:
+        for _ in range(l.v):
+            swap(l,l.n)
+    elif l.v < 0:
+        for _ in range(-l.v):
+            swap(l.p,l)
+
+S = 0
+s = V0
+for i in range(3000+1):
+    if i in [1000,2000,3000]:
+        S += s.v
+    s = s.n
+print(S)
diff --git a/d20/part2.py b/d20/part2.py
new file mode 100644
index 0000000..e33aa6d
--- /dev/null
+++ b/d20/part2.py
@@ -0,0 +1,51 @@
+from __future__ import annotations
+import sys
+from dataclasses import dataclass
+
+@dataclass
+class E:
+    v: int
+    p: E
+    n: E
+
+DEK = 811589153
+V0 = None
+p = None
+L = []
+for l in sys.stdin.read().splitlines():
+    e = E(int(l)*DEK,p,None)
+    L.append(e)
+    if l == "0":
+        V0 = e
+    if p is not None:
+        p.n = e
+    p = e
+L[-1].n = L[0]
+L[0].p = L[-1]
+
+def swap(l,m):
+    k = l.p
+    n = m.n
+    k.n = m
+    n.p = l
+    l.n = n
+    m.p = k
+    l.p = m
+    m.n = l
+
+for _ in range(10):
+    for l in L:
+        if l.v > 0:
+            for _ in range(l.v%(len(L)-1)):
+                swap(l,l.n)
+        elif l.v < 0:
+            for _ in range(-l.v%(len(L)-1)):
+                swap(l.p,l)
+
+S = 0
+s = V0
+for i in range(3000+1):
+    if i in [1000,2000,3000]:
+        S += s.v
+    s = s.n
+print(S)