uva 11143

  1 #include<cstdio>
  2 #include<cstring>
  3 #include<algorithm>
  4 #define maxn 5100
  5 #include<queue>
  6 using namespace std;
  7 
  8 struct node
  9 {
 10     int x,y;
 11     int id;
 12     bool operator<(const node &t)const
 13     {
 14         return y>t.y;
 15     }
 16 } hang[maxn],lie[maxn];
 17 
 18 bool cmp(const node &a,const node &b)
 19 {
 20     return a.x<b.x;
 21 }
 22 
 23 int h[maxn],l[maxn];
 24 
 25 priority_queue<node>q;
 26 
 27 int main()
 28 {
 29     int n;
 30     while(scanf("%d",&n)&&n)
 31     {
 32         for(int i=0; i<n; i++)
 33         {
 34             scanf("%d%d%d%d",&hang[i].x,&lie[i].x,&hang[i].y,&lie[i].y);
 35             hang[i].id=lie[i].id=i;
 36             h[i]=0;
 37             l[i]=0;
 38         }
 39         sort(hang,hang+n,cmp);
 40         int cur=0;
 41         int timer=1;
 42         bool flag=1;
 43         while(!q.empty())q.pop();
 44         while(1)
 45         {
 46             while(cur<n&&hang[cur].x<=timer)q.push(hang[cur++]);
 47             if(timer<=n&&q.empty())
 48                 {
 49                     flag=0;
 50                     break;
 51                 }
 52             node v=q.top();
 53             q.pop();
 54             if(timer<v.x||timer>v.y)
 55             {
 56                 flag=0;
 57                 break;
 58             }
 59             h[v.id]=timer;
 60             timer++;
 61             if(timer>n)break;
 62         }
 63         if(flag)
 64         {
 65             sort(lie,lie+n,cmp);
 66             cur=0;
 67             timer=1;
 68             while(!q.empty())q.pop();
 69             while(1)
 70             {
 71                 while(cur<n&&lie[cur].x<=timer)q.push(lie[cur++]);
 72                 if(timer<=n&&q.empty())
 73                 {
 74                     flag=0;
 75                     break;
 76                 }
 77                 node v=q.top();
 78                 q.pop();
 79                 if(timer<v.x||timer>v.y)
 80                 {
 81                     flag=0;
 82                     break;
 83                 }
 84                 l[v.id]=timer;
 85                 timer++;
 86                 if(timer>n)break;
 87             }
 88         }
 89         for(int i=0;i<n;i++)
 90             if(l[i]==0||h[i]==0)
 91             {
 92                 flag=0;
 93                 break;
 94             }
 95         if(flag)
 96         {
 97             for(int i=0; i<n; i++)
 98                 printf("%d %d\n",h[i],l[i]);
 99         }
100         else puts("IMPOSSIBLE");
101     }
102     return 0;
103 }