#include <bits/stdc++.h>

using namespace std;

pair<int, int> box[6];//注意书写方式
int i;

int main() {
    while (1) {
        for (i = 0; i < 6; i++) {
            if (scanf("%d%d", &box[i].first, &box[i].second) != 2) return 0;
            if (box[i].first > box[i].second)
                swap(box[i].first, box[i].second);
        }
        sort(box, box + 6);//我试了一下，此处排序是按照先first递增，其次second递增排序
        puts(box[0].first == box[1].first && box[1].first == box[2].first && box[2].first == box[3].first &&
             box[0].second == box[1].second && box[1].second == box[4].first && box[4].first == box[5].first &&
             box[2].second == box[3].second && box[3].second == box[4].second && box[4].second == box[5].second ?
             "POSSIBLE" : "IMPOSSIBLE");
    }
}