def quick_sort(q,l,r):

if l>=r:
    return

i = l-1
j = r+1
p = q[l+r>>1]

while i<j:
    while True:
        i+=1
        if q[i]>=p:
            break
    while True:
        j-=1
        if q[j]<=p:
            break
    if i<j:
        q[i],q[j] = q[j],q[i]

quick_sort(q,l,j)
quick_sort(q,j+1,r)