BAEKJOON_14501

import java.io.*;
import java.util.*;


public class Main {
    static int[] t;
    static int[] p;
    static int ans=0;
    static int N;

    public static void recursion(int day, int sum){
        if(day==N+1){
            if(ans<sum)ans=sum;
            return;
        }
        if(day>N+1){
            return;
        }
        recursion(day+1,sum);
        recursion(day + t[day], sum + p[day]);
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw =new BufferedWriter(new OutputStreamWriter(System.out));

        N = Integer.parseInt(br.readLine());

        t=new int[N+1];   //N=7이면  배열은 크기가 8
        p=new int[N+1];
        StringTokenizer st;
        for(int i=1; i<=N; i++){
            st= new StringTokenizer(br.readLine());
            t[i] = Integer.parseInt(st.nextToken());
            p[i] = Integer.parseInt(st.nextToken());
        }

        recursion(1,0);
        bw.write(String.valueOf(ans));
        bw.flush();bw.close();
    }
}