#include <bits/stdc++.h>
using namespace std;

int first = 1;

int win(int n, int k) {
    if(n % (k + 1) == 1) return 1 - first;
    else return first;
}

int main() {
    int out = 0;
    for(int i=0;i<1000;i++) {
        int n, k;
        cin >> n >> k;
        int winner = win(n, k);
        if(winner) {
            out++;
            first = 0;
        }
        else first = 1;
    }

    cout << out << '\n';

    return 0;
}