#encoding=utf-8
a=[
[1,2,3,4],
[5,6,7,8],
[9,10,11,12],
[13,14,15,16]
]
#所有元素的和
sum=0
for i in a:
for j in i:
sum+=j
print sum
#一条对角线
sum_diagonal=0
for i in range(len(a)):
sum_diagonal+=a[i][i]
print sum_diagonal
#反对角线
back_diagonal=0
for i in range(len(a)):
back_diagonal+=a[i][len(a)-1-i]
print back_diagonal