import java.util.*;
import java.io.*;
import java.io.BufferedReader;
import java.awt.Point;

public class mowing{
	public static final String TASKNAME = "mowing";
	public static long mod= 1000000007;
	public static Debug db;

	public static void main(String[] args) throws IOException {
//		InputReader in = new InputReader(System.in);
//		PrintWriter out = new PrintWriter(System.out);
		InputReader in = new InputReader(new FileInputStream(TASKNAME+".in"));
		PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(TASKNAME+".out")));
		Autocompletion solver = new Autocompletion();
		db=new Debug(System.getSecurityManager()==null);
		solver.solve(1, in, out);
		out.close();
	}
	static class Autocompletion {
		boolean vert=true;//even is vert
		public void solve(int testNumber, InputReader in, PrintWriter out) {
			int n=in.nextInt();
			int t=in.nextInt();
			TreeSet<Triple> sweep=new TreeSet<Triple>();//stores x val and id, negative for removing hor
			long count=0;
			int arr[][]=new int[n][2];
			for(int i=0;i<n;i++) {
				arr[i][0]=in.nextInt();
				arr[i][1]=in.nextInt();
			}
			if(arr[0][0]==arr[1][0]) {//first is vert
				vert=false;
			}
			for(int i=1;i<n;i++) {
				if((i%2==0)^vert) {//hor
					sweep.add(new Triple(arr[i][0],arr[i][1],-i));//- to remove
					sweep.add(new Triple(arr[i-1][0],arr[i][1],i));
				}
				else {

					sweep.add(new Triple(arr[i][0],arr[i-1][1],i));
				}
			}
			int maxN=(int) Math.pow(10,9)+1;
			bit2d bit=new bit2d(maxN,maxN);
			while(!sweep.isEmpty()) {
				Triple x=sweep.pollFirst();
				if(x.z%2==0 ^ vert) {//hor
					if(x.z<0) {
//						bit.updateBIT(x, -x.z, -1);
					}
					else {
						bit.updateBIT(x.y, x.z, 1);
					}
				}
				else {
					int y1=Math.min(arr[x.z][1], arr[x.z-1][1]);
					int y2=Math.max(arr[x.z][1], arr[x.z-1][1]);
					count+=bit.getRect(y1, 0, y2,x.z-t)+bit.getRect(y1, x.z+t, y2, maxN);
				}
			}

			out.println(count);
		}

	}

	static class bit2d {
		int bit[][];
		int n;
		int m;
		bit2d(int n, int m){
			bit=new int[n+2][m+2];
			this.n=n;
			this.m=m;
		}
		void updateBIT(int x,int y, int val)  {
			for (; x <= n; x += (x & -x))  {
				// updates the 1D bits
				for (; y <= m; y += (y & -y))
					bit[x][y] += val;
			}
			return;
		}
		// sum from (0, 0) to (x, y)
		int getSum(int x, int y)  {
			int sum = 0;
			for(; x > 0; x -= x&-x){
				for(; y > 0; y -= y&-y){
					sum +=bit[x][y];
				}
			}
			return sum;
		}
		int getRect(int x1, int y1, int x2, int y2) {
			int ans = getSum(x2, y2)-getSum(x2, y1 - 1)-getSum(x1 - 1, y2)+getSum(x1 - 1, y1 - 1);
			return ans;
		}
	}

	static class Pair implements Comparable<Pair>{
		int x;
		int y;
		Pair(int a, int b){
			x=a;
			y=b;
		}
		@Override
		public int compareTo(Pair arg0) {
			if(arg0.x!=x)return x-arg0.x;
			return y-arg0.y;
		}
	}
	static class Triple implements Comparable<Triple>{
		int x;
		int y;
		int z;
		Triple(int a, int b, int c){
			x=a;
			y=b;
			z=c;
		}
		@Override
		public int compareTo(Triple arg0) {
			if(arg0.x!=x)return x-arg0.x;
			return y-arg0.y;
		}
	}

	static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
        public long nextLong() {
        	return Long.parseLong(next());
        }
        public int[] nextIntArr(int n) {
        	int arr[]=new int[n];
        	for(int i=0;i<n;i++) {
        		arr[i]=this.nextInt();
        	}
        	return arr;
        }
    }
	public static class Debug {
        private boolean allowDebug;

        public Debug(boolean allowDebug) {
            this.allowDebug = allowDebug;
        }

        private void outputName(String name) {
            System.out.print(name + " = ");
        }

        public void debug(String name, int x) {
            if (!allowDebug) {
                return;
            }

            outputName(name);
            System.out.println("" + x);
        }

        public void debug(String name, long x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println("" + x);
        }

        public void debug(String name, double x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println("" + x);
        }

        public void debug(String name, int[] x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println(Arrays.toString(x));
        }

        public void debug(String name, long[] x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println(Arrays.toString(x));
        }

        public void debug(String name, double[] x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println(Arrays.toString(x));
        }

        public void debug(String name, Object x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println("" + x);
        }

        public void debug(String name, Object... x) {
            if (!allowDebug) {
                return;
            }
            outputName(name);
            System.out.println(Arrays.deepToString(x));
        }
    }
}