object Main {
	def main(args: Array[String]): Unit = {
		val N = readInt()
		val arrayA = Array.ofDim[Int](2, N)
		var max = 0
		for (i <- 0 to 1) {
			for (j <- 0 to N) {
				arrayA(i)(j) = readInt()
			}
		}
		for (i <- 0 to N) {
			var current = 0
			for (j <- 0 to i) {
				current += arrayA(0)(j)
			}
			for (j <- i to N) {
				current += arrayA(1)(j)
			}
			if (current > max) {
				max = current
			}
		}
		println(max) 
	}
}