输入n个数字,是否存在两个数字之和等于给定的k,
存在输出yes,否则输出no
第一行n和k(n<=105),(k<=109)(n<=10^5),(k<=10^9)(n<=105),(k<=109)
n个数字aia_iai,(0<=ai<=109)(0<=a_i<=10^9)(0<=ai<=109)
yes或者no
4 4 1 2 3 4
yes