#include <iostream>
#include <map>
using namespace std;
int a,b;
map<int,int> mp,mp2;
int main()
{
	bool ok=1;
	for(int i=1;i<=6;i++)
	{
		cin>>a>>b;
		mp[a]++;mp[b]++;mp2[a]++;
		if(a!=b)mp2[b]++;
	}
	for(map<int,int> :: iterator p=mp.begin();p!=mp.end();p++)
	if(p->second%4!=0||(p->second==4&&mp2[p->first]!=4))ok=0;
	cout<<(ok==1?"POSSIBLE":"IMPOSSIBLE")<<endl; 
}