N, K = gets.split(" ").map{|s| s.to_i}

a = gets.split(" ").map{|s| s.to_i}
b = gets.split(" ").map{|s| s.to_i}

dp = Array.new(N+1) {Array.new(K+1) {Array.new(2)}}

0.upto(K) {|j|
	dp[0][j][0] = -Float::INFINITY
	dp[0][j][1] = ""
}

dp[0][0][0] = 0

1.upto(N) {|i|
	0.upto(K) {|j|
		dp[i][j][0] = -Float::INFINITY
		dp[i][j][1] = ""
	}
	0.upto([i,K].min) {|j|
		dp[i][j] = [j > 0 ? [dp[i-1][j-1][0] + a[i-1], dp[i-1][j-1][1] + "A"] : [-Float::INFINITY, ""],
		[dp[i-1][j][0] + b[i-1], dp[i-1][j][1] + "B"]].max
	}
}

puts dp[N][K][1]