#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e5+10;
signed main()
{
	int n;cin>>n;
	map<int,int>mp;priority_queue<int,vector<int>,greater<int>>q;
	for(int i=1;i<=n;i++)
	{
		int x,y;cin>>x>>y;
		if(!mp[x])q.push(x);
		mp[x]+=y;
	}
	int ans=0;
	while(!q.empty())
	{
		int x=q.top();q.pop();
		if(mp[x]&1)ans++;if(mp[x]==1)continue;
		if(!mp[x*2])q.push(x*2);
		mp[x*2]+=mp[x]/2;
	}
	cout<<ans;
	return 0;
}