diff --git a/src/util.py b/src/util.py
--- a/src/util.py
+++ b/src/util.py
@@ -1,11 +1,25 @@
-def progress(i, n, i0=0):
-	def _progress(i,n,i0):
-		return 100*(i+1-i0)//(n-i0)
+class Progress:
+	def __init__(self,n,i0=0):
+		self._n=n
+		self._i0=i0
+		self._i=i0
+		self._last=""
+
+	def p(self,i):
+		i0=self._i0
+		n=self._n
 
-	if n<i0:
-		i*=-1
-		n*=-1
-		i0*=-1
-	assert i0<=i<n, (i0,i,n)
-	percentage=_progress(i,n,i0)
-	print("{0}%".format(percentage),end="\r")
+		assert i0<=i<n or n<i<=i0, (i0,i,n)
+		percentage=Progress._p(i,n,i0)
+		res="{0}%".format(percentage)
+		if res!=self._last:
+			print(res,end="\r")
+			self._last=res
+
+	def done(self):
+		print("100%")
+
+	@staticmethod
+	def _p(i,n,i0):
+		_1=1 if n>=i0 else -1
+		return 100*(i+_1-i0)//(n-i0)