fix typo

app.py

@@ -107,7 +107,7 @@ class BZHStableSignatureDemo(object):
         #result = "resolution = %dx%d  p-value = %e" % (img.size[0], img.size[1], pvalue))
         result = "No watermark detected."
         chances = int(1 / pvalue + 1)
-        rpv = 10**int(math.log10(p-value))
+        rpv = 10**int(math.log10(pvalue))
         if pvalue < 1e-3:
             result = "Watermark detected with low confidence (p-value < %e)" % rpv # (< 1/%d chances of being wrong)" % chances
         if pvalue < 1e-9: