NZEC in a problem as it is working fine

why am I getting NZEC in [ ] problem?

my solution

from sys import stdin
for _ in range(int(input())):
    n = int(stdin.readline())

Python3 is using floating point arithmetic for the operator /. That means the (huge) integer n*(n+1) is transformed to a float before dividing. Besides precision problems this yields an overflow if the number is too large.

Either use Python2 or use the operator // instead of /.

Thanks Sir