def intSum(arcs,A):
s = 0
for a in A:
for arc in arcs:
i = intervalIntersection(arc[1:],a)
if i: s += i[1] - i[0]
return s
def intSum(arcs,A):
s = 0
for a in A:
for arc in arcs:
i = intervalIntersection(arc[1:],a)
if i: s += i[1] - i[0]
return s