1 //#define LOCAL
 2 #include <iostream>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 
 7 const int maxn = 100000;
 8 int a[maxn + 10][11];
 9 int max(int a, int b, int c)
10 {
11     a = max(a, b);
12     return max(a, c);
13 }
14 
15 int main(void)
16 {
17     #ifdef LOCAL
18         freopen("1176in.txt", "r", stdin);
19     #endif
20 
21     int n;
22     while(scanf("%d", &n) == 1 && n)
23     {
24         memset(a, 0, sizeof(a));
25         int i, Tmax = 0;    //用来记录T的最大值 
26         for(i = 0; i < n; ++i)
27         {
28             int x, T;
29             scanf("%d %d", &x, &T);
30             ++a[T][x];
31             if(T > Tmax)
32                 Tmax = T;
33         }
34 
35         int j;
36         for(i = Tmax; i >= 1; --i)
37             for(j = 0; j <= 10; ++j)
38             {
39                 if(j == 0)
40                 {
41                     a[i - 1][j] += max(a[i][j], a[i][j + 1]);
42                     continue;
43                 }
44                 if(j == 10)
45                 {
46                     a[i - 1][j] += max(a[i][j - 1], a[i][j]);
47                     continue;
48                 }
49                 a[i - 1][j] += max(a[i][j - 1], a[i][j], a[i][j + 1]);
50             }
51 
52         cout << a[0][5] << endl;
53     }
54     return 0;
55 }