1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 const int maxn=110000;
 7 
 8 int dp[maxn][12];
 9 int v[maxn][12];
10 
11 int max1(int a,int b,int c,int d)
12 {
13     int temp=a>b?a:b;
14     int temp1=temp>c?temp:c;
15     return temp1>d?temp1:d;
16 }
17 
18 int main()
19 {
20     //freopen("in.txt","r",stdin);
21     int i,j,n,time;
22     while(scanf("%d",&n),n)
23     {
24         memset(v,0,sizeof(v));
25         memset(dp,0,sizeof(dp));
26         time=0;
27         for(i=0;i<n;i++)
28         {
29             int a,b;
30             scanf("%d%d",&a,&b);
31             time=max(time,b);
32             v[b][a+1]++;
33         }
34         for(i=time;i>=0;i--)
35         for(j=1;j<=11;j++)
36         dp[i][j]=max1(dp[i][j],v[i][j]+dp[i+1][j-1],dp[i+1][j]+v[i][j],dp[i+1][j+1]+v[i][j]);
37         printf("%d\n",dp[0][6]);
38     }
39     return 0;
40 }