#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<iostream>
using namespace std;
struct sky
{
	int num,time,dat;
};
sky a[200000];
int n,ans;
bool comp(sky a,sky b)
{
	return a.num<b.num || (a.num==b.num && a.time>b.time);
}
int main()
{
	freopen("boarding.in","r",stdin);
	freopen("boarding.out","w",stdout);
	scanf("%d",&n);
	for (int i=1;i<=n;i++)
	{
		scanf("%d%d",&a[i].num,&a[i].time);
		a[i].dat=n-i;
	}
	ans=1;
	ans=a[1].dat+ans;
	sort(a+1,a+n+1,comp);
	for (int i=1;i<=n;i++)
	{
		if (a[i].dat!=a[i-1].dat) ans+=a[i].time;
	}
	if (a[1].dat==0) ans++;
	printf("%d",ans);
}