#include <bits/stdc++.h>
using namespace std;

int main() {
	int N,K,count=0;
	for(int i=0;i<1000;i++){
		cin>>N>>K;
		N-=1;
		while(N-K>1){
			N=N-K-1;
		}
		if(N<=K){
			count++;
		}
	}
	cout<<count<<endl;
	return 0;
}