1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <queue>
 8 #include <stack>
 9 #include <map>
10 #include <string>
11 #include <set>
12 #define ms(a,b) memset((a),(b),sizeof((a)))
13 using namespace std;
14 typedef long long LL;
15 const double EPS = 1e-8;
16 const int INF = 2e9;
17 const LL LNF = 2e18;
18 const int MAXN = 1e5+10;
19 
20 int a[MAXN][12], dp[MAXN][12];
21 int n;
22 
23 int main()
24 {
25     while(scanf("%d", &n) &&n)
26     {
27         ms(a, 0);
28         for(int i = 1; i<=n; i++)
29         {
30             int x, t;
31             scanf("%d%d", &x, &t);
32             a[t][x]++;
33         }
34 
35         ms(dp,-1);
36         dp[0][5] = 0;
37         int ans = -INF;
38         for(int i = 1; i<=1e5; i++) //时间
39         for(int j = 0; j<=10; j++)  //地点
40         {
41             if(dp[i-1][j]!=-1)  //留在原地
42                 dp[i][j] = max( dp[i][j], dp[i-1][j]+a[i][j] );
43             if(j!=0 && dp[i-1][j-1]!=-1)    //从左边走过来
44                 dp[i][j] = max( dp[i][j], dp[i-1][j-1]+a[i][j] );
45             if(j!=10 && dp[i-1][j+1]!=-1)   //从右边走过来
46                 dp[i][j] = max( dp[i][j], dp[i-1][j+1]+a[i][j] );
47 
48             ans = max(ans, dp[i][j]);
49         }
50 
51         printf("%d\n", ans);
52     }
53 }