#include <algorithm>
#include <iostream>
#include <sstream>
#include <fstream>
#include <math.h>
#include <vector>
#include <bitset>
#include <string>
#include <stack>
#include <queue>
#include <map>
#include <set>

/*
#pragma warning(disable:4244 4800)
#include <gmp/mpirxx.h>
// MPZ_CLASS
// MPQ_CLASS
// MPF_CLASS
#pragma warning(default:4244 4800)
*/

#define _CRT_SECURE_NO_DEPRECATE

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vi2;
typedef pair<int, int> ii;
typedef vector<ii> vii;

#define FOR(i, a, b) \
for (int i = int(a); i < int(b); i++)
#define FORi(i, c) \
for (auto i = (c).begin(); i != (c).end(); i++)

string name = "mowing";
ifstream in( name+".in" );
ofstream out( name+".out" );

// START



int main()
{
    // BEGIN
    int n, t;
    in >> n >> t;

    vi Xcoords( n );
    vi Ycoords( n );
    for( int i = 0; i < n; i++ )
        in >> Xcoords[i] >> Ycoords[i];

    int fh = (Ycoords[0] == Ycoords[1]) ? 1 : 0;

    int ANS = 0;

    for( int i = n-1; i > 0; i-- )
    {
        for( int j = i-t-1; j > 0; j-- )
        {
            if( i % 2 == fh ) // if horiz
            {
                int bigx = max( Xcoords[i], Xcoords[i-1] );
                int smallx = min( Xcoords[i], Xcoords[i-1] );
                int bigy = max( Ycoords[j], Ycoords[j-1] );
                int smally = min( Ycoords[j], Ycoords[j-1] );

                if( Ycoords[i] > smally && Ycoords[i] < bigy &&
                    Xcoords[j] > smallx && Xcoords[j] < bigx )
                {
                    ANS++;
                }
            } else // if vert
            {
                int bigy = max( Ycoords[i], Ycoords[i-1] );
                int smally = min( Ycoords[i], Ycoords[i-1] );
                int bigx = max( Xcoords[j], Xcoords[j-1] );
                int smallx = min( Xcoords[j], Xcoords[j-1] );

                if( Ycoords[j] > smally && Ycoords[j] < bigy &&
                    Xcoords[i] > smallx && Xcoords[i] < bigx )
                {
                    ANS++;
                }
            }
        }
    }

    out << ANS;

    // END
    in.close();
    out.close();
    return 0;
}