1 //2016.8.5
 2 //HDU1176
 3 #include<iostream>
 4 #include<cstdio>
 5 #include<cstring>
 6 
 7 using namespace std;
 8 
 9 int mapp[100005][12], dp[100005][12];
10 int dx[4] = {1, 0, -1, 0};
11 int dy[4] = {0, -1, 0, 1};
12 
13 int main()
14 {
15     int n, x, t, tt;
16     while(cin>>n&&n)
17     {
18         tt = 0;
19         memset(mapp, 0, sizeof(mapp));
20         for(int i = 0; i < n; i++)
21         {
22             scanf("%d%d", &x, &t);
23             mapp[t][x]++;//转换为图，时间为纵轴，１１个位置为横轴
24             if(t>tt)tt = t;
25         }
26         for(int i = 0; i <= 10; i++)
27           dp[1][i] = 0;
28         dp[1][5] = mapp[1][5];
29         dp[1][4] = mapp[1][4];
30         dp[1][6] = mapp[1][6];//时间为１时只能走三个点
31         for(int i = 2; i <= tt; i++)
32         {
33             mapp[i][11] = 0;
34             for(int j = 0; j <= 10; j++)
35             {
36                 if(j==0)dp[i][j] = max(dp[i-1][j], dp[i-1][j+1]);
37                 else dp[i][j] = max(dp[i-1][j-1], max(dp[i-1][j], dp[i-1][j+1]));
38                 dp[i][j]+=mapp[i][j];
39             }
40         }
41         int ans = 0;
42         for(int i = 0; i <= 10; i++)
43         {
44             if(dp[tt][i]>ans)ans = dp[tt][i];
45         }
46         cout<<ans<<endl;
47     }
48 
49     return 0; 
50 }