Score : $600$ points
We have $N$ cards arranged in a row on a table. For each $i = 1, 2, \ldots, N$, the $i$-th card has an integer $A_i$ written on the front and an integer $B_i$ written on the back. Initially, every card is placed face up.
Takahashi will choose any number of cards he likes (possibly zero) and flip them. Then, he will be happy if the following condition is satisfied:
Determine whether it is possible for Takahashi to be happy.
Input is given from Standard Input in the following format:
$N$ $A_1$ $B_1$ $A_2$ $B_2$ $\vdots$ $A_N$ $B_N$
If it is possible for Takahashi to be happy, print Yes
; otherwise, print No
.
3 2 5 10 9 4 8
Yes
Initially, we see integers $2$, $10$, and $4$.
If we flip the first and second cards, we will see $5$, $9$, and $4$, which will make Takahashi happy. Thus, we should print Yes
.
2 10 100 1000 10000
No
There is no way to flip cards to make Takahashi happy, so we should print No
.