1 #include <iostream>
    2 #include <fstream>
    3 
    4 using namespace std;
    5 
    6 int arr[100000];
    7 
    8 int sort(const void*a ,const void* b)
    9 {
   10   int* aa=(int*)a;
   11   int* bb=(int*)b;
   12   if (*aa>*bb) return 1;
   13   if (*aa<*bb) return -1;
   14   return 0;
   15 }
   16 int main()
   17 {
   18   //freopen("b.in","r",stdin);
   19   int n;
   20   while (cin>>n)
   21     {
   22       if (n==0)
   23         return 0;
   24       int i=0;
   25       for (i=0;i<n;i++)
   26         {
   27           cin>>arr[i];
   28         }
   29       qsort(arr,n,sizeof(int),sort);
   30       bool cando=true;
   31       for (i=1;i<n;i++)
   32         if (arr[i]-arr[i-1]>200)
   33           {
   34             cando=false;
   35             break;
   36           }
   37       if (1422-arr[n-1]>100) cando=false;
   38       if (cando) cout<<"POSSIBLE"<<endl;
   39       else cout<<"IMPOSSIBLE"<<endl;
   40 
   41     }
   42   return 0;
   43 }