Update app.py

app.py

@@ -83,7 +83,7 @@ def calculate_probabilities(A, B, C, AB, AC, BC, ABC, U):
 
 def draw_venn(A, B, C, AB, AC, BC, ABC):
     plt.figure(figsize=(10,10))
-    venn = venn3(subsets=(A - AB - AC + ABC, B - AB - BC + ABC, AB - ABC, C- AC - BC + ABC, AC - ABC, BC - ABC, ABC), set_labels=('A', 'B', 'C'))
+    venn = venn3(subsets=(max(0, A - AB - AC + ABC), max(0,B - AB - BC + ABC), max(0,AB - ABC), max(0,C- AC - BC + ABC), max(AC - ABC, 0), max(BC - ABC,0), ABC), set_labels=('A', 'B', 'C'))
     img = BytesIO()
     plt.savefig(img, format='png')
     img.seek(0)