My code runs fine but I am getting runtime error NZEC. Any help?
n = int(input())
while n:
str = input()
res = []
row_count = len(str)/n
for i in range(n):
for j in range(int(row_count)):
if(j%2==0):
res.append(str[j*n+i])
else:
res.append(str[(j+1)*n+i-(2*i+1)])
print(res)