Hi, Admins.
Please, add these case:
N > 5*10^4
a[i] = 1, for i = 1.. N-1, and
a[N] = 10^9

Q = N
p[i] = i,  x[i] = i

For example:
77888
1 1 1 1 1 1 .... 1 1 77888
77888
1 1
2 2
3 3
4 4
5 5
...
77888 77888

my solution takes 0.031 seconds.