//********************************
//*???????.cpp   **
//*?????? 1200012768 **
//*???2012.10.12  **
//********************************
int main()               
{
     int n, h = 0, t = 0;  //????????????????????? 
//   cout << "????????n?";
     cin >> n;
     int sbp[n], dbp[n];  //???n????????n??????? 
     for (int i = 0; i < n; i++)
         cin >> sbp[i] >> dbp[i]; //????????? 
     for (int i = 0; i < n; i++)
     {
         if (sbp[i] >= 90 && sbp[i] <= 140
             && dbp[i] >=60 && dbp[i] <= 90)
         {
            h += 1;  //???????????? 1 
            t =(t > h ? t : h);  //?????? 
         } 
         else
            h = 0;    //?????????????????????????? 
     }
//   cout << "?????????????";
     cout << t << endl;
     return 0;
} 
