import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

public class NetworkPacket {

    public static class Request {
        public int arrivalTime;
        public int processTime;

        public Request(int arrivalTime, int processTime) {
            this.arrivalTime = arrivalTime;
            this.processTime = processTime;
        }

    }

    public static class Response {
        public boolean dropped;
        public int startTime;

        public Response(boolean dropped, int startTime) {
            this.dropped = dropped;
            this.startTime = startTime;
        }
    }

    public static class Buffer {
        private int size;
        private ArrayList<Integer> finishTime = new ArrayList<Integer>();

        public Buffer(int size) {
            this.size = size;
        }
        public Response processRequests(Request request) {
            // write your code here
            if (this.size == 0)
            return new Response(false,-1);
            else {
                if (finishTime.size() == 0)
            }
        }
    }
    private static ArrayList<Request> ReadQueries(Scanner scanner) throws IOException {
        int requests_count = scanner.nextInt();
        ArrayList<Request> requests = new ArrayList<Request>();
        for (int i = 0; i < requests_count; ++i) {
            int arrival_time = scanner.nextInt();
            int process_time = scanner.nextInt();
            requests.add(new Request(arrival_time, process_time));
        }
        return requests;
    }

    public static ArrayList<Response> processRequests(ArrayList<Request> requests, Buffer buf) {
        ArrayList<Response> responses = new ArrayList<>();
        for (int i = 0; i < requests.size(); i++) {
           responses.add(buf.processRequests(requests.get(i)));
        }
        return responses;
    }
    private static void PrintResponses(ArrayList<Response> responses) {
        for (int i = 0; i < responses.size(); ++i) {
            Response response = responses.get(i);
            if (response.dropped) {
                System.out.println(-1);
            } else {
                System.out.println(response.startTime);
            }
        }
    }

    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);

        int buffer_max_size = scanner.nextInt();
        Buffer buffer = new Buffer(buffer_max_size);

        ArrayList<Request> requests = ReadQueries(scanner);
        ArrayList<Response> responses = processRequests(requests, buffer);
        PrintResponses(responses);
    }
}