#include <iostream>
#include <cstring>	// require memset
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;

bool is_win(int n, int k){
	return (n - 1) % (k + 1) != 0;	// 先攻が勝つ true 後攻が勝つ false
}

int n[1000], k[1000];
bool game[1000];	// 先攻が勝利する true 敗退する false
bool res[1000];

int main()
{
	memset (n, 0, sizeof(n));
	memset (k, 0, sizeof(k));
	memset (game, false, sizeof(game));
	memset (res, false, sizeof(res));

	ios_base::sync_with_stdio(0);
	rep (i, 1000){
		cin >> n[i] >> k[i];
		game[i] = is_win(n[i],k[i]);
	} // end rep

	bool  batting_first = true;
	res[0] = game[0];
	for (int i = 1; i < 1000; ++i){
		if (!res[i-1]){
			batting_first = game[i];
		}else{
			batting_first = !game[i];
		} // end if
		res[i] = !(batting_first ^ game[i]);
	} // end for

	int ans = count(res, res+1000, true);
	cout << ans << endl;
	
	return 0;
}