import java.util.*;
/*** @version Ver 1.0* @date 2025/6/20* @description 观看文艺汇演*/
public class WatchMovie {public static void main(String[] args) {Scanner sc = new Scanner(System.in);int num = Integer.parseInt(sc.nextLine());List<Movie> movies = new ArrayList<>(num);for (int i = 0; i < num; i++) {int[] array = Arrays.stream(sc.nextLine().split("\\s+")).mapToInt(Integer::parseInt).toArray();movies.add(new Movie(array[0],array[1]));}// 按照结束时间 升序排序movies.sort((m1,m2)->{return m1.getEndTime() - m2.getEndTime();});solve(movies);}private static void solve(List<Movie> movies) {//720 120//840 120//0 60//90 60int count = 0;int tempTime = 0;//记录上一场演出的结束时间+去下一场演出花费的时间for (int i = 0; i < movies.size(); i++) {Movie current = movies.get(i);if(current.getStartTime() >= tempTime){//下一场演出开始时间>=tempTime，才能看演出tempTime = current.getEndTime()+15;count++;}}System.out.println(count);}
}class Movie{private Integer startTime;private Integer endTime;public Movie() {}public Integer getStartTime() {return startTime;}public void setStartTime(Integer startTime) {this.startTime = startTime;}public Integer getEndTime() {return endTime;}public void setEndTime(Integer endTime) {this.endTime = endTime;}public Movie(Integer startTime, Integer dual) {this.startTime = startTime;this.endTime = startTime + dual;}
}