diff --git a/main.py b/main.py
index 1dae8a5..5ce3da6 100644
--- a/main.py
+++ b/main.py
@@ -37,6 +37,26 @@ Cp = []; # Positions of customers
 Ci = []; # Needs of customers
 # {product number: qt}
 
+# Debug
+
+assert(len(Dp) == len(Di) == len(Dd) == len(Da) == D)
+assert(len(Pw) == P)
+assert(len(Wp) == len(Wi) == W)
+assert(len(Cp) == len(Ci) == C)
+
+#def droneInfos(d):
+#    print("- Drone", d, "carries", ", ".join([p + ": " + q + "×" + Dw[p] for 
+
+def showGrid():
+    for y in range(Y):
+        for x in range(X):
+            if (x, y) in Wp:
+                print("W", end="")
+            if (x, y) in Cp:
+                print("C", end="")
+            else:
+                print("·", end="")
+
 # Utilities
 def distance(A, B):
     return math.ceil(sqrt(pow((B[0] - A[0], 2) + pow(B[1] - A[1], 2))))
@@ -89,7 +109,7 @@ def newTurn():
     print("--- Turn", t)
     for d in Da:
         wait(d)
-    assert(Da.len == 0)
+    assert(len(Da) == 0)
     for d in range(D):
         if Dd[d] <= t:
             Da.push(d)