def sort(a,n):
    for i in range(0,n):
        for j in range(i+1):
            if a[i]<a[j]:
                t=a[i]
                a[i]=a[j]
                a[j]=t
n=input()
a=[]
i=0
j=0
q=0
for i in range(0,n):
    x=int(raw_input())
    a.append(x)
sort(a,n)
for i in range(0,n-1):
    if a[i+1]==a[i]+1:
        q=q+1
if q==n-1:
    print "YES"
The above is the solution to a Hackerearth problem, being new to python i am facing this NZEC error which bothers me a lot as i got no solution for this error.
Can someone please tell me why am i getting this error and whats the solution for the same
 
     
    