#include <iostream>
#include <cstdio>
#include <algorithm>
#include <set>
#include <cctype>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
using namespace std;
const int maxn=100010;
const int INF=0x3f3f3f3f;
int dp[maxn][11],n,max_time;
int three_max(int x,int y,int z)
{
	return max(x,max(y,z));
}
void solve()
{
	for(int i=max_time⑴;i>=0;i--)
	{
		for(int j=0;j<=10;j++)
		{
			if(j==0)
				dp[i][j]+=max(dp[i+1][j],dp[i+1][j+1]);
			else if(j==10)
				dp[i][j]+=max(dp[i+1][j],dp[i+1][j⑴]);
			else
				dp[i][j]+=three_max(dp[i+1][j⑴],dp[i+1][j],dp[i+1][j+1]);
		}
	}
	printf("%d
",dp[0][5]);
}
int main()
{
	int x,T;
    while(scanf("%d",&n)!=EOF&&n)
	{
		memset(dp,0,sizeof(dp));
		max_time=-INF;
		for(int i=0;i<n;i++)
		{
			scanf("%d%d",&x,&T);
			++dp[T][x];
			max_time=max(max_time,T);
		}
		solve();
	}
    return 0;
}