diff --git a/d25/part1.py b/d25/part1.py
new file mode 100644
index 0000000..1882ec4
--- /dev/null
+++ b/d25/part1.py
@@ -0,0 +1,21 @@
+import sys
+
+def snafu2dec(s:str)->int:
+    D = {'0': 0, '1':1, '2':2, '-':-1, '=':-2 }
+    n = 0
+    for (i,c) in enumerate(reversed(s)):
+        n += 5**i * D[c]
+    return n
+
+def dec2snafu(n:int) -> str:
+    d = "=-012"
+    l = []
+    while n>0:
+        r=(n+2)%5-2
+        l.append(d[r+2])
+        n = (n-r) // 5
+    return "".join(reversed(l))
+        
+        
+if __name__ == "__main__":
+    print(dec2snafu(sum(snafu2dec(l) for l in sys.stdin.read().splitlines())))