WA in ALASKA....help!

[sid_iiita]

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
    long int i,n;
    int a,j;
   vector <int> v;
    do{
    	v.clear();
        scanf("%ld",&n);
        if(n == 0){
            break;
        }
        for(i=0;i<n;i++){
            scanf("%d",&a);
            v.push_back(a);
    }
sort(v.begin(),v.end());
        int p = 0;
        for(i=0;i<n-1;i++){
        if((v[i+1] - v[i]) > 200){
            p = 1;
            printf("IMPOSSIBLE\n");
        }
    }
    if(2*(1422 - v[n-1]) > 200){
        p = 1;
            printf("IMPOSSIBLE\n");
    }

    if(p == 0){
        printf("POSSIBLE\n");
    }
}while(n != 0);

return 0;
}