using System;
using System.Collections;
using System.Collections.Generic;
using System.Numerics;
using System.Text;
using System.IO;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		int turn=0;
		int[] Player=new int[2];
		using(FastIn rd = new FastIn()){
			for(int i=0;i<1000;i++){
				BigInteger x=rd.ReadBI();
				BigInteger y=rd.ReadBI();
				if((x-1)%(y+1)==0){
					Player[turn^1]++;
					turn^=1;
				}else{
					Player[turn]++;
				}
			}
		}
		Console.WriteLine(Player[0]);
		
		
		
	}

	public Sol(){
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
	static BigInteger[] rba(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>BigInteger.Parse(e));}
}


class FastIn:IDisposable {
	int Size;
	byte[] Mem;
	int ptr;
	int rsize;
	bool unfinished;
	Stream stdin;
	void Init(int n) {
		Size = n;
		Mem = new byte[Size];
		rsize=(stdin=Console.OpenStandardInput()).Read(Mem, 0, Size);
		ptr = 0;
		unfinished=(rsize == Size);
	}
	void Next() {
		if (unfinished == false) return;
		rsize=stdin.Read(Mem, 0, Size);
		ptr = 0;
		unfinished = (rsize == Size);
	}
	
	~FastIn(){
		stdin.Dispose();
	}
	void IDisposable.Dispose(){
		stdin.Dispose();
	}
	public void Dispose(){
		stdin.Dispose();
	}
	
	public FastIn() {
		Init(100000);
	}
	public FastIn(int n) {
		Init(n);
	}
	public int ReadInt() {
		int ret = 0;
		int sig = 1;
		while (ptr < rsize && Mem[ptr] != ' ' && Mem[ptr] != '\n' && Mem[ptr] != '\r' ) {
			if(ret==0 && Mem[ptr] == '-'){
				sig *= -1; ptr++; continue;
			}
			ret = ret * 10 + Mem[ptr++] - '0';
			if (ptr == Size) Next();
		}
		while (ptr < rsize && (Mem[ptr] == ' ' || Mem[ptr] == '\n' || Mem[ptr] == '\r') ) {
			ptr++;
			if (ptr == Size) Next();
		}
		return ret*sig;
	}
	public BigInteger ReadBI() {
		BigInteger ret = 0;
		BigInteger sig = 1;
		while (ptr < rsize && Mem[ptr] != ' ' && Mem[ptr] != '\n' && Mem[ptr] != '\r' ) {
			if(ret==0 && Mem[ptr] == '-'){
				sig *= -1; ptr++; continue;
			}
			ret = ret * 10 + Mem[ptr++] - '0';
			if (ptr == Size) Next();
		}
		while (ptr < rsize && (Mem[ptr] == ' ' || Mem[ptr] == '\n' || Mem[ptr] == '\r') ) {
			ptr++;
			if (ptr == Size) Next();
		}
		return ret*sig;
	}
	public long ReadLong() {
		long ret = 0;
		long sig = 1;
		while (ptr < rsize && Mem[ptr] != ' ' && Mem[ptr] != '\n' && Mem[ptr] != '\r' ) {
			if(ret==0 && Mem[ptr] == '-'){
				sig *= -1; ptr++; continue;
			}
			ret = ret * 10 + Mem[ptr++] - '0';
			if (ptr == Size) Next();
		}
		while (ptr < rsize &&  (Mem[ptr] == ' ' || Mem[ptr] == '\n' || Mem[ptr] == '\r')  ) {
			ptr++;
			if (ptr == Size) Next();
		}
		return ret*sig;
	}
	public String ReadStr() {
		//2byte文字はNG
		StringBuilder sb = new StringBuilder();
		while (ptr < rsize && Mem[ptr] != ' ' && Mem[ptr] != '\n' && Mem[ptr] != '\r') {
			sb.Append((char)Mem[ptr++]);
			if (ptr == Size && unfinished) Next();
		}
		while (ptr < rsize &&  (Mem[ptr] == ' ' || Mem[ptr] == '\n' || Mem[ptr] == '\r') ) {
			ptr++;
			if (ptr == Size && unfinished) Next();
		}
		return sb.ToString();
	}
	public String ReadLine() {
		//極力使わない(split/parseするくらいなら上をつかう）
		StringBuilder sb = new StringBuilder();
		while (ptr < rsize && Mem[ptr] != '\n' && Mem[ptr] != '\r') {
			sb.Append((char)Mem[ptr++]);
			if (ptr == Size && unfinished) Next();
		}
		while (ptr < rsize &&  (Mem[ptr] == ' ' || Mem[ptr] == '\n' || Mem[ptr] == '\r')) {
			ptr++;
			if (ptr == Size && unfinished) Next();
		}
		return sb.ToString();
	}
}