class Solution():
    def turn(self,A):
        res = list(zip(*A))
        res = res[::-1]
        return res

    def printmatrix(self,A):
        ans = []
        while(A):
            ans+=(A.pop(0))
            if not A or not A[0]:
                break
            A = self.turn(A)
        return ans



#test
s = Solution()
A = [[1,2,3,4],[5,6,7,8],[9,10,11,12],[13,14,15,16]]
print(s.printmatrix(A))
#test