import java.util.*;
public class Main {
static int n;
static int[] t = new int[15];
static int[] p = new int[15];
static int[] dp = new int[16];
static int maxValue;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
n = sc.nextInt();
for (int i = 0; i < n; i++) {
t[i] = sc.nextInt();
p[i] = sc.nextInt();
}
for (int i = n - 1; i >= 0; i--) {
int time = t[i] + i;
if (time <= n) {
dp[i] = Math.max(p[i] + dp[time], maxValue);
maxValue = dp[i];
}
else dp[i] = maxValue;
}
System.out.println(maxValue);
}
}