f = lambda x:sum(r[i]*r[~i]for i,r in enumerate(x))
print f([[-1, 1], [-2, 1]])
print f([[824, -65], [-814, -741]])
print f([[-1, -8, 4], [4, 0, -5], [-3, 5, 2]])
print f([[0, -1, 0], [1, 0, 2], [1, 0, 1]])
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