#include <iostream>
#include <algorithm>

using namespace std;

int win[1001];
int memo[2][1001];

int dfs(int f,int m){
	if (m == 1000)return 0;
	if (memo[f][m] != -1)return memo[f][m];

	if (win[m] == f){
		return memo[f][m] = min(dfs(f, m + 1), dfs(1-f, m + 1)) + 1;
	}
	else{
		return memo[f][m] = max(dfs(f, m + 1), dfs(1-f, m + 1));
	}
}

int main()
{

	for (int i = 0; i < 1000;i++){
		int n, k;
		cin >> n >> k;
		win[i] = ((n % (k + 1) == 1) ? 1 : 0);
		memo[0][i] = memo[1][i] = -1;
	}
	cout << dfs(0, 0) << endl;

	return 0;
}