import java.util.ArrayList;
import java.util.List;

public class Start {
	public static List<Mark> marks = new ArrayList<Mark>();

	public static void calculateMark() {
		double percent_total = 0;
		double average_total = 0;

		for (Mark mark : marks) {
			int percent = mark.getPercent();
			percent_total += percent;

			int score = mark.getScore();
			double average = (score * percent) / 100;
			average_total += average;
		}

		double final_average = Math
				.round((average_total * 100 / percent_total) * 100) / 100;

		System.out.println(final_average);
	}

	public static void main(String[] args) {
		marks.add(new Mark(80, 80));
		marks.add(new Mark(70, 20));
		calculateMark();
	}

	static class Mark {
		private int score, percent;

		public Mark(int score, int percent) {
			this.score = score;
			this.percent = percent;
		}

		public int getScore() {
			return score;
		}

		public int getPercent() {
			return percent;
		}
	}
}