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.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.StringTokenizer;

public class q1 {
    public static MyScanner in = new MyScanner();
    public static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out), true);
    public static MyViewer view = new MyViewer();
    public static BufferedWriter log = new BufferedWriter(new OutputStreamWriter(System.out));
    public static Random rand = new Random(System.currentTimeMillis());
    public static class Pair<A, B> {
        private final A first;
        private final B second;

        public Pair(A first, B second) {
            super();
            this.first = first;
            this.second = second;
        }

        public int hashCode() {
            int hashFirst = first != null ? first.hashCode() : 0;
            int hashSecond = second != null ? second.hashCode() : 0;

            return (hashFirst + hashSecond) * hashSecond + hashFirst;
        }

        public boolean equals(Object other) {
            if (other instanceof Pair) {
                Pair otherPair = (Pair) other;
                return
                        ((  this.first == otherPair.first ||
                                ( this.first != null && otherPair.first != null &&
                                        this.first.equals(otherPair.first))) &&
                                (  this.second == otherPair.second ||
                                        ( this.second != null && otherPair.second != null &&
                                                this.second.equals(otherPair.second))) );
            }

            return false;
        }

        public String toString()
        {
            return "(" + first + ", " + second + ")";
        }

        public A getFirst() {
            return first;
        }

        public B getSecond() {
            return second;
        }
    }

    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;
        private boolean randomInput = false;
        private Random rand;

        void randomInput(boolean r) {
            randomInput = r;
            rand = new Random(System.currentTimeMillis());
            //rand = new Random(42);
        }

        public MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        public MyScanner(InputStream is) {
            br = new BufferedReader(new InputStreamReader(is));
        }

        public String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public int nextInt(int val) {
            return randomInput ? val : Integer.parseInt(next());
        }

        public int nextInt(int low, int high) {
            if (randomInput) {
                return rand.nextInt(high - low + 1) + low;
            } else {
                return Integer.parseInt(next());
            }
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        long nextLong(long val) {
            return randomInput ? val : Long.parseLong(next());
        }

        long nextLong(long low, long high) {
            if (randomInput) {
                return low+((long)(rand.nextDouble()*(high-low + 1)));
            } else {
                return Long.parseLong(next());
            }
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        int[] arrayInt(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextInt();
            }
            return a;
        }

        int[] arrayInt(int n, int low, int high) {
            int[] a = new int[n];
            if (randomInput) {
                for (int i = 0; i < n; i++) {
                    a[i] = rand.nextInt(high - low + 1) + low;
                }
            } else {
                for (int i = 0; i < n; i++) {
                    a[i] = nextInt();
                }
            }
            return a;
        }

        ArrayList<Integer> list(int n) {
            ArrayList<Integer> a = new ArrayList<Integer>(n);
            for (int i = 0; i < n; i++) {
                a.add(nextInt());
            }
            return a;
        }

        ArrayList<Integer> list(int n, int low, int high) {
            ArrayList<Integer> a = new ArrayList<Integer>(n);
            if (randomInput) {
                for (int i = 0; i < n; i++) {
                    a.add(rand.nextInt(high - low + 1) + low);
                }
            } else {
                for (int i = 0; i < n; i++) {
                    a.add(nextInt());
                }
            }
            return a;
        }

        long[] arrayLong(int n) {
            long[] a = new long[n];
            for (int i = 0; i < n; i++) {
                a[i] = nextLong();
            }
            return a;
        }

        long[] arrayLong(int n, long low, long high) {
            long[] a = new long[n];
            if (randomInput) {
                for (int i = 0; i < n; i++) {
                    double r = rand.nextDouble();
                    a[i] = (long)(r * (double) (high - low + 1)) + low;
                    if( a[i] == 0) {
                        out.println("Ouch : " + r );
                    }
                }
            } else {
                for (int i = 0; i < n; i++) {
                    a[i] = nextLong();
                }
            }
            return a;
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

        void close() {
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        ArrayList<ArrayList<Integer>> randomTree(int n) {
            ArrayList<ArrayList<Integer>> edges = new ArrayList<>();
            for (int i = 0; i < n; i++) {
                edges.add(new ArrayList<>());
            }

            for (int i = 1; i < n; i++) {
                int par = rand.nextInt(i);
                edges.get(par).add(i);
            }
            return edges;
        }
    }

    static class MyViewer {
        private static boolean  print = true;

        public void on() {
            print = true;
        }

        public void off() {
            print = false;
        }

        public <T extends List> void list(T a) {
            if (!print) return;
            if( a == null) {
                out.println("List: NULL");
                return;
            }
            if( a.size() == 0) {
                out.println("List: []");
                return;
            }
            out.print("List: [" + a.get(0));
            for (int i = 1; i < a.size(); i++) {
                out.print(", " + a.get(i));
            }
            out.println("] Len: " + a.size());
        }

        public <T extends Number> void array(T[] a) {
            if (!print) return;
            if( a == null) {
                out.println("Array: NULL");
                return;
            }
            if( a.length == 0) {
                out.println("Array: []");
                return;
            }
            out.print("Array: [" + a[0]);
            for (int i = 1; i < a.length; i++) {
                out.print(", " + a[i]);
            }
            out.println("] Len: " + a.length);
        }

        public void array(boolean[] a) {
            if (!print) return;if( a == null) {
                out.println("boolean[]: NULL");
                return;
            }
            if( a.length == 0) {
                out.println("boolean[]: Len: 0");
                return;
            }
            out.print("boolean[] Len: " + a.length + " [");
            for (boolean x : a) {
                out.print(x + ", ");
            }
            out.println("\b\b]");
        }

//        public void array(int[] a) {
//            if (!print) return;
//
//            if( a == null) {
//                out.println("Array: NULL");
//                return;
//            }
//            if( a.length == 0) {
//                out.println("Array: []");
//                return;
//            }
//            out.print("int[] Len: " + a.length + " [");
//            for (int x : a) {
//                out.print(x + ", ");
//            }
//            out.println("\b\b]");
//        }
//
//        public void array(long[] a) {
//            if (!print) return;
//            if( a == null) {
//                out.println("Array: NULL");
//                return;
//            }
//            if( a.length == 0) {
//                out.println("Array: []");
//                return;
//            }
//            out.print("long Array: [");
//            for (long x : a) {
//                out.print(x + ", ");
//            }
//            out.println("\b\b] Len: " + a.length);
//        }

        public <T extends Number> void matrix(T[][] a, int cutoffRowCol) {
            if (cutoffRowCol == 0)
                cutoffRowCol = Integer.MAX_VALUE;
            if( a == null) {
                out.println("Matrix: NULL");
                return;
            }
            for (int i = 0; i < a.length; i++) {
                if (i < cutoffRowCol) {
                    printMatrixRow(a[i], cutoffRowCol);
                } else {
                    out.println("     ...");
                    printMatrixRow(a[a.length - 1], cutoffRowCol);
                    break;
                }
            }
        }

//        public void matrix(long[][] a, long cutoff) {
//            if (cutoff == 0)
//                cutoff = Long.MAX_VALUE;
//            if( a == null) {
//                out.println("Matrix: NULL");
//                return;
//            }
//            for (int i = 0; i < a.length; i++) {
//                if (i < cutoff) {
//                    printMatrixRow(a[i], cutoff);
//                } else {
//                    out.println("     ...");
//                    printMatrixRow(a[a.length - 1], cutoff);
//                    break;
//                }
//            }
//        }

        public void matrix(boolean[][] a, int cutoffRowCol) {
            if (cutoffRowCol == 0)
                cutoffRowCol = Integer.MAX_VALUE;
            if( a == null) {
                out.println("Matrix: NULL");
                return;
            }
            for (int i = 0; i < a.length; i++) {
                if (i < cutoffRowCol) {
                    printMatrixRow(a[i], cutoffRowCol);
                } else {
                    out.println("     ...");
                    printMatrixRow(a[a.length - 1], cutoffRowCol);
                    break;
                }
            }
        }

        private <T extends Number> void printMatrixRow(T[] a, int cutoff) {
            for (int j = 0; j < a.length; j++) {
                if (j < cutoff) {
                    out.printf("%6d  ", a[j]);
                } else {
                    out.printf(" ... %6d", a[a.length - 1]);
                    break;
                }
            }
            out.println();
        }

//        private void printMatrixRow(long[] a, long cutoff) {
//            for (int j = 0; j < a.length; j++) {
//                if (j < cutoff) {
//                    out.printf("%6d  ", a[j]);
//                } else {
//                    out.printf(" ... %6d", a[a.length - 1]);
//                    break;
//                }
//            }
//            out.println();
//        }

        private void printMatrixRow(boolean[] a, int cutoff) {
            for (int j = 0; j < a.length; j++) {
                if (j < cutoff) {
                    out.print(a[j] ? "T " : "F ");
                } else {
                    out.print(" ... " + (a[a.length - 1] ? "T" : "F"));
                    break;
                }
            }
            out.println();
        }

    }

    public static void main(String[] args) throws IOException {
        int n = in.nextInt();
        int L = in.nextInt();
        int a = in.nextInt();

        int[] t = new int[n];
        int[] l = new int[n];

        for(int i = 0 ; i < n;i ++ ) {
            t[i] = in.nextInt();
            l[i] = in.nextInt();
        }

        long ans = 0;
        int pre = 0;
        for ( int i = 0 ;i < n;i ++ ) {
            int b = (t[i] - pre) / a;
            ans += b;
            pre = t[i] + l[i];
        }

        int b= (L - pre)/a;
        ans += b;

        out.println(ans);

        log.flush();
        in.close();
    }
}
