#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	int x = 1000;
	vector<long long> n(x), k(x);

	for(int i=0; i<x; i++){
		cin >> n[i] >> k[i];
	}

	vector<vector<int>> dp(x+1, vector<int>(2, 0));
	vector<vector<bool>> ok(x+1, vector<bool>(2,false));
	ok[0][0] = true;

	int ans = 0;
	for(int i=0; i<x; i++){
		bool win = false;
		if(n[i] <= k[i]) win = true;
		else if((n[i]-1) % (k[i]+1) != 0) win = true;

		if(ok[i][0]){
			if(win){
				dp[i+1][1] = max(dp[i+1][1], dp[i+1][0] + 1);
				ok[i+1][1] = true;
			}
			dp[i+1][0] = max(dp[i+1][0], dp[i+1][0]);
			ok[i+1][0] = true;
		}


		if(ok[i][0]){
			if(win){
				dp[i+1][0] = min(dp[i+1][0], dp[i+1][1]);
				ok[i+1][0] = true;
			}
			dp[i+1][1] = min(dp[i+1][1], dp[i+1][0]);
			ok[i+1][1] = true;
		}

	}
	ans = max(dp[x][0], dp[x][1]);
	cout << ans << endl;
	return 0;
}