#include <iostream>
#include <vector>
#include <tuple>
#include <algorithm>
using namespace std;
using ll = long long;

int main() {
    int res = 0;
    int turn = 0; // 0: you
    for(int i=0; i<1000; ++i) {
        ll N, K;
        cin >> N >> K;
        if(turn == 0) {
            if(N <= K || N % (K+1) != 0) {
                res++;
                turn = 1;
            } else {
                turn = 0;
            }
        } else {
            if(N <= K || N % (K+1) != 0) {
                turn = 0;
            } else {
                res++;
                turn = 1;
            }
        }
    }
    cout << res << endl;
}