import java.util.*;

public class PriorityQueueUse {

public static int solution(int max, List<Lecture> arr, int n) {

int answer = 0;

Collections.sort(arr);

PriorityQueue<Integer> queue = new PriorityQueue<>(Collections.reverseOrder());

int j = 0;

for (int i = max; i > 0; i--) {

for (; j < n; j++) {

if (arr.get(j).period < i) {

break;

}

queue.offer(arr.get(j).money);

}

if (!queue.isEmpty()) {

answer += queue.poll();

}

}

return answer;

}

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

int n = scanner.nextInt();

int max = Integer.MIN_VALUE;

List<Lecture> arr = new ArrayList<>();

for (int i = 0; i < n; i++) {

int m = scanner.nextInt();

int p = scanner.nextInt();

if (p > max) {

max = p;

}

arr.add(new Lecture(m, p));

}

System.out.println(solution(max, arr, n));

}

public static class Lecture implements Comparable<Lecture> {

int money;

int period;

public Lecture(int money, int period) {

this.money = money;

this.period = period;

}

@Override

public int compareTo(Lecture o) {

return o.period - this.period;

}

}

}