#include <algorithm>
#include <vector>
#include <cfloat>
#include <string>
#include <cmath>
#include <set>
#include <cstdlib>
#include <map>
#include <ctime>
#include <iomanip>
#include <functional>
#include <deque>
#include <iostream>
#include <cstring>
#include <queue>
#include <cstdio>
#include <stack>
#include <climits>
#include <sys/time.h>
#include <cctype>

using namespace std;

typedef long long ll;

int main() {
  int n, k;
  int ans = 0;
  bool b = true;
  for (int i = 0; i < 1000; i++) {
    scanf("%d %d", &n, &k);
    if ((n+1)%(k+1) == 1) {
      if (b) {
	ans++;
      }
      b = false;
    }
  }
  printf("%d\n", ans);
}