import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] t = new int[n];
		int[] p = new int[n];
		for (int a = 0; a < n; a++) {
			t[a] = sc.nextInt();
			p[a] = sc.nextInt();
		}
		int answer = 0;
		for (int a = 1; a < 32768; a++) {
			int newanswer = 0;
			for (int b = 0; b < n; b++) {
				if ((a & (1 << b)) != 0) {
					if (b + t[b] <= n) {
						newanswer += p[b];
						b += t[b] - 1;
					}
				}
			}
			answer = Math.max(answer, newanswer);
		}
		System.out.println(answer);
		sc.close();
	}
}