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

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        int[] bandage = {5, 1, 5};
        int health = 30;
        int[][] attacks = {{2, 10}, {9, 15}, {10, 5}, {11, 5}};
        
        int[] bandage_1 = {3, 2, 7};
        int health_1 = 20;
        int[][] attacks_1 = {{1, 15}, {5, 16}, {8, 6}};
        
        //System.out.println(solution(bandage, health, attacks));
        System.out.println(solution(bandage_1, health_1, attacks_1));
    }
    
    public static int solution(int[] bandage, int health, int[][] attacks) {
        int curent_health = health;
        int loop = 0;
        int at_t = 0;
        
        System.out.println("0 / "+curent_health+" / "+loop);
        
        for (int i = 1; i <= attacks[attacks.length - 1][0]; i++) {
            if(i == attacks[at_t][0]) {
                curent_health -= attacks[at_t][1];
                System.out.println(i+" / "+curent_health+"(" + (-attacks[at_t][1]) + ") / "+loop);
                if(curent_health <= 0) {
                    curent_health = -1;
                    break;
                }
                loop = 0;
                at_t++;
                continue;
            }
            
            
            loop++;
            curent_health += bandage[1];
            if(loop == bandage[0]) {
                curent_health += bandage[2];
            }
            if(curent_health > health) {
                curent_health = health;
                loop = 0;
            }
            
            System.out.println(i+" / "+curent_health+"(+"+(bandage[1] + (loop == bandage[0] ? bandage[2] : 0))+") / "+loop);
        }
        
        return curent_health;
    }
}