pr1=[2,3,1,2,4]
pr2=[3,4,10,11,12]
n=5
xlst=[0] * n
for i in range(len(xlst)):
if (n-sum(xlst[:i]))>0:
xn=n-sum(xlst[:i])
else:
xn=0
xlst[i]=min(xn, pr1[i], pr2[i]-sum(xlst[:i]))
