Vasya has recently got a job as a cashier at a local store. His day at work is L minutes long. Vasya has already memorized n regular customers, the i-th of which comes after t_{i} minutes after the beginning of the day, and his service consumes l_{i} minutes. It is guaranteed that no customer will arrive while Vasya is servicing another customer. 

Vasya is a bit lazy, so he likes taking smoke breaks for a minutes each. Those breaks may go one after another, but Vasya must be present at work during all the time periods he must serve regular customers, otherwise one of them may alert his boss. What is the maximum number of breaks Vasya can take during the day?

Input

The first line contains three integers n, L and a (0 ≤ n ≤ 10^{5}, 1 ≤ L ≤ 10^{9}, 1 ≤ a ≤ L).

The i-th of the next n lines contains two integers t_{i} and l_{i} (0 ≤ t_{i} ≤ L - 1, 1 ≤ l_{i} ≤ L). It is guaranteed that t_{i} + l_{i} ≤ t_{i + 1} and t_{n} + l_{n} ≤ L.

Output

Output one integer — the maximum number of breaks.

Examples

Input

2 11 3
0 1
1 1


Output

3

Input

0 5 2


Output

2

Input

1 3 2
1 2


Output

0

Note

In the first sample Vasya can take 3 breaks starting after 2, 5 and 8 minutes after the beginning of the day.

In the second sample Vasya can take 2 breaks starting after 0 and 2 minutes after the beginning of the day.

In the third sample Vasya can't take any breaks.
import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class a{ 
     static int[] count,count1,count2;
     static long[] arr;
     static char[] ch,ch1;
     static int[] darr,farr;
     static Character[][] mat,mat1;
     static long x,h;
     static long maxl;
     static double dec;
     static String s;
     static long minl;
     static int mx = (int)1e6;
     static long mod = 998244353l;
     // static int minl = -1;
     static long n;
     // static int n,n1,n2;
     static long a,l,g;
     static long b;
     static long c;
     static long d;
     static long y,z;
     static int m;
     static long k;
     static int q;
     static String[] str,str1;
     static Set<Integer> set,set1;
     static List<Integer> list,list1,list2;
     static LinkedList<Character> ll;
     static Map<Integer,Integer> map;
     static StringBuilder sb,sb1,sb2;

     public static void solve(){

        FastScanner sc = new FastScanner();
        n = sc.nextLong();
        l = sc.nextLong();
        a = sc.nextLong();

        long beg = 0;
        long sum = 0;
        for(int i =  0;  i < n ; i++){
            long t = sc.nextLong();
            long b = sc.nextLong();
            sum += (t-beg)/a;
            beg = t+b;
        }

        sum += (l-beg)/a;
        System.out.println(sum);

     }

     public static void main(String[] args) {

            FastScanner sc = new FastScanner();
            // Scanner sc = new Scanner(System.in);
            // int t = sc.nextInt();
            int t = 1;
            while(t > 0){
                
                // x = sc.nextLong();
                // y = sc.nextLong();
                // z = sc.nextLong();
                
                // a = sc.nextLong();
                // b = sc.nextLong();
                // c = sc.nextLong();
                // d = sc.nextLong();
                // n = sc.nextLong();
                // n = sc.nextInt();
                // m = sc.nextInt();
                // x = sc.nextLong();
                // y = sc.nextLong();
                // x = sc.newxtLong();

                // y = sc.nextLong();
                // n1 = sc.nextInt();
                // n = sc.nextLong();

                // k = sc.nextLong();

                // ch = sc.next().toCharArray();
                // ch1 = sc.next().toCharArray();

                // m = sc.nextLong();
                // k = sc.nextLong();

                // arr = new long[n];
                // for(int i = 0; i < n ; i++){
                //     arr[i] = sc.nextLong();
                // }
                 
                // darr = new int[n];
                // for(int i = 0; i < n ; i++){
                //     darr[i] = sc.nextInt();
                // }
                
                // n1 = sc.nextInt();
                //  darr = new long[n1];
                //  for(int i = 0; i < n1 ; i++){
                //      darr[i] = sc.nextLong();
                //  }

                // mat = new Character[n][n];
                // for(int i = 0 ; i < n ; i++){
                //     String s = sc.next();
                //     for(int j = 0 ; j < n ; j++){
                //         mat[i][j] = s.charAt(j);
                //     }
                // }
                // str = new String[n];
                // for(int i = 0 ; i < n ; i++)
                //     str[i] = sc.next();

                // System.out.println(solve()?"Yes":"No");
                 solve();       
                 // System.out.println(solve());

                 t -= 1;
            }

     }

    public static int log(long n){

         if(n == 0 || n == 1)
             return 0;

         if(n == 2)
             return 1;

         double num = Math.log(n);
         double den = Math.log(2);

         if(den == 0)
             return 0;

         return (int)(num/den);
     }

     public static long gcd(long a,long b){

        if(b%a == 0)
            return a;

        return gcd(b%a,a);

     }

     // public static void swap(int i,int j){
     //     long temp = arr[j];
     //     arr[j] = arr[i];
     //     arr[i] = temp;
     // } 

    static final Random random=new Random();
    
    static void ruffleSort(long[] a) {
        int n=a.length;//shuffle, then sort 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            long temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        Arrays.sort(a);
    }

    static class Node{
        int first;
        int second;
        Node(int f,int s){
            this.first = f;
            this.second = s;
        }
    }

     static class FastScanner {

                BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
                StringTokenizer st=new StringTokenizer("");
                String next() {
                        while (!st.hasMoreTokens())
                                try {
                                        st=new StringTokenizer(br.readLine());
                                } catch (IOException e) {
                                        e.printStackTrace();
                                }
                        return st.nextToken();
                }
                
                int nextInt() {
                        return Integer.parseInt(next());
                }
                int[] readArray(int n) {
                        int[] a=new int[n];
                        for (int i=0; i<n; i++) a[i]=nextInt();
                        return a;
                }
                long nextLong() {
                        return Long.parseLong(next());
                }
        }

}