diff --git a/day15/sol.py b/day15/sol.py
index 1b72943..f154faf 100644
--- a/day15/sol.py
+++ b/day15/sol.py
@@ -23,27 +23,48 @@ for sx,sy,bx,by in data:
 
 print(len(none))
 
-# find the closest sensor to x,y within dist
-def mindist(x,y):
-    for sx,sy,bx,by in data:
-        dx = abs(sx-bx)
-        dy = abs(sy-by)
-        dist = dx+dy
-        dx = abs(x-sx)
-        dy = abs(y-sy)
-        d2 = dx+dy
-        if d2 <= dist:
-            yield dist-d2
+objs = []
+for sx,sy,bx,by in data:
+    dist = abs(sx-bx) + abs(sy-by)
+    objs.append((sx,sy,dist))
 
-for y in range(0, 4000000+1):
+# find the closest sensor to x,y within dist
+def mindist(x,y, objs=objs):
+    for sx,sy,dist in yobjs:
+        d = abs(x-sx) + abs(y-sy)
+        if d <= dist:
+            yield dist-d
+
+# y=2573243
+Y = 2500000
+Y = 0
+
+objs.sort()
+
+for y in range(Y, 4000000+1):
+    ranges = []
+    for sx,sy,dist in objs:
+        dy = abs(y-sy)
+        if dy <= dist:
+            dx = dist - dy
+            ranges.append((sx-dx,sx+dx))
+    ranges.sort()
     x = 0
-    while x <= 4000000:
-        for d in mindist(x,y):
-            x += d+1
+    for a,b in ranges:
+        if b < x:
+            continue
+        if x < a:
+            print(x,y,"=",x*4000000+y)
             break
-        else:
-            print(x,y)
+        x = b+1
+        if x > 4000000:
             break
-    if y % 10000 == 0:
+        #try:
+        #    d = max(mindist(x,y,objs=yobjs))
+        #    x += d+1
+        #except ValueError:
+        #    print(x,y)
+        #    break
+    if y % 100000 == 0:
         print(y)