#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <string>
#include <tuple>
#include <functional>
#include <numeric>
#include <cmath>
#include <iomanip>
#include <map>
#include <random>
//#include "toollib.h"
#define INT_MAX 2147483647
#define Loop(i, n) for(int i = 0; i < (int)n; i++)
#pragma warning (disable:4018)

using namespace std;
typedef long long int lint;

//***** Main Program *****

int main() {
	vector<pair<int, int>> input;
	Loop(i, 1000) cin >> input[i].first >> input[i].second;
	int mode = 0, ret = 0;
	Loop(i, 1000) {
		if (mode == 0) {
			if (input[i].first % (input[i].second + 1) != 0) {
				ret++;
				mode = 1;
			}
		}
		if (mode == 1) {
			if (input[i].first % (input[i].second + 1) != 0) {
				mode = 0;
			}
			else {
				ret++;
			}
		}
	}
	cout << ret << endl;
	return 0;
}