#include <cstdio>
#include <stdio.h>
#include <vector>
#include <cmath>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main()
{
	vector <int> w(6);
	vector <int> h(6);
	vector <vector <int> > same(10000,vector<int> (10000));
	vector <int> amount(10000,0);
	for (int i =0;i<6;++i) {
        cin>> w[i]>>h[i];
        same[w[i]][h[i]]++;
        same[h[i]][w[i]]++;
        amount[w[i]]=w[i];
        amount[h[i]]=h[i];
	}
	int result=0;
	for (int i =0;i<amount.size();++i) {
        if (amount[i]!=0) result++;
	}
    if (result == 1) {
        cout << "POSSIBLE";
        return 0;
    }
    if (result >3) {
        cout << "IMPOSSIBLE";
        return 0;
    }
    bool pr=true;
    if (result ==3) {
        for (int i =0;i<6;++i) {
            if (same[w[i]][h[i]]!=2)
            pr=false;
        }
        if (pr) cout << "POSSIBLE"; else cout << "IMPOSSIBLE";
        return 0;
    }
    int p=0;
    if (result ==2) {
        for (int i=0; i<6;++i) {
            if (same[w[i]][h[i]]==4)
                p++;
            if (same[w[i]][h[i]]==2) p++;
        }
        if (p==2) cout << "POSSIBLE"; else cout << "IMPOSSIBLE";
        return 0;
    }
}