1 #include<iostream>
 2 #include<string>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<vector>
 8 #include<iomanip>
 9 #include<queue>
10 using namespace std;
11 int f[11][100001];
12 int max(int a,int b,int c)
13 {
14     return a>b?(a>c?a:c):(b>c?b:c);
15 }
16 int main()
17 {
18     int n,x,t;
19     while(scanf("%d",&n))
20     {
21         if(n==0) break;
22         memset(f,0,sizeof(f));
23         int maxt=0;
24         while(n--)
25         {
26             scanf("%d%d",&x,&t);
27             f[x][t]++;
28             if(t>maxt) maxt=t;
29         }
30         for(int i=maxt-1;i>=0;i--)
31         {
32             f[0][i]+=max(f[0][i+1],f[1][i+1],0);
33             f[10][i]+=max(f[10][i+1],f[9][i+1],0);
34             for(int j=1;j<=9;j++)
35             {
36                 f[j][i]+=max(f[j][i+1],f[j-1][i+1],f[j+1][i+1]);
37             }
38         }
39         printf("%d\n",f[5][0]);
40     }
41     return 0;
42 }