What are the common reasons for NZEC Errors in Python?

Can somebody point out the cause for NZEC error in this two problems?. If somebody could list out the errors with example it would be a great help for all the pythonists.

1.Alphacode:http://www.spoj.com/SPOJ/problems/ACODE/

dic = {}
def main():
	while True:
		line = int(raw_input())
		if line == 0:break
		print dp(str(line))
		dic.clear()
def dp(line):
	if line in dic:
		return dic[line]
	else:
		if len(line) > 2:
			a = chk(line[0])*dp(line[1:]) + chk(line[:2])*dp(line[2:])
		elif len(line) > 1:
			a = chk(line[0])*dp(line[1]) + chk(line)
		else:
			a = chk(line)
	dic[line] = a
	return a
def chk(word):
	if word[0] == '0':
		return 0
	if int(word) <= 26 and int(word) > 0:
		return 1
	else:
		return 0
main()

2.Training for final http://www.spoj.com/SPOJ/problems/TRIKA/1

from sys import stdin
def main():
	n, m = map(int,stdin.readline().rstrip().split())
	x, y = map(int,stdin.readline().rstrip().split())
	arr = []
	for r in range(n):
		row = map(int,stdin.readline().rstrip().split())
		arr.append(row)
	i, j = 1, 0	
	while i	<= n-1:
		arr[i][j] = arr[i-1][j] - arr[i][j]
		i+=1
	i, j = 0, 1
	while j <= m-1:
		arr[i][j] = arr[i][j-1] - arr[i][j]
		j+=1
	i = 1
	while i <= n-1:
		j = 1	
		while j <= m-1:
			arr[i][j] = max(arr[i-1][j],arr[i][j-1]) - arr[i][j]
			j+=1
		i+=1
	if arr[i-1][j-1]<0:print 'N'
	else:
		 print 'Y ' + str(arr[i-1][j-1]) 
main()