nzec error in python.

hey! This is the code for the trianglesum problem. I'm getting an nzec error. I though it is due to some extra spaces problem. But even after using split() it doesn't work. I've checked the forum but couldn't find an answer to my problem. Any kind of help will be deeply appreciated.

t = raw_input().split()
for i in range(int(t[0])):
    n = []
    tx = raw_input().split()
    for k in range(int(tx[0])):
        n.append(raw_input().split()[0])
    summ = int(n[0])
    x = 0
    for l in range(1, int(tx[0])) :
        if int(n[l][x]) > int(n[l][x+1]):
            summ = summ + int(n[l][x])
        else:
            summ = summ + int(n[l][x+1])
            x = x+1
    print summ