// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;

queue<int>q;

int nedge=0,p[1000010],nex[1000010],head[1000010],rp[1000010];

int dist[200010],vis[200010],n,m,s,t,g,l;

inline void addedge(int x,int y){

	p[++nedge]=y;nex[nedge]=head[x];head[x]=nedge;

}

inline void spfa(){

	memset(dist,0x3f,sizeof dist);

	dist[1]=0;q.push(1);vis[1]=1;

	while(!q.empty()){

		int now=q.front();q.pop();

		for(int k=head[now];k;k=nex[k])if(dist[p[k]]>dist[now]+1){

			dist[p[k]]=dist[now]+1;

			if(!vis[p[k]]){vis[p[k]]=1;q.push(p[k]);}

		}vis[now]=0;

	}

}

int main()

{

	ios::sync_with_stdio(0);

	int n,m;cin>>n>>m;

	for(int i=1;i<=m;i++){

		int x,y;cin>>x>>y;

		addedge(x,y);

	}

	spfa();

	if(dist[n]>2)puts("IMPOSSIBLE");

	else puts("POSSIBLE");

}

// Faster C++ solution for the same problem (measured speedup: 1.2850304088042235x):
#include <bits/stdc++.h>

using namespace std;



//===============typedef

typedef long long ll;

typedef vector<int> vi;

typedef vector<ll> vl;

typedef vector< vi > vvi;

typedef pair<int, int> ii;

typedef vector<ii> vii;

typedef vector<vii> vvii;

typedef set<int> si;

typedef map<string, int> msi;



/*

using namespace __gnu_pbds;



#include <ext/pb_ds/assoc_container.hpp> // Common file

#include <ext/pb_ds/tree_policy.hpp> // Including 

template<typename T>

using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

template<typename F, typename S>

using ordered_map = tree<F, S, less<F>, rb_tree_tag, tree_order_statistics_node_update>;

*/





//=================Constant

const ll MOD=1e9+7;

const ll inf=10000000;



//=============define

#define cln(a) memset(a,0,sizeof a);

#define clni(a) memset(a,inf,sizeof a);

#define all(x) x.begin(), x.end()

#define tr(container, it) for(typeof(container.begin()) it = container.begin(); it != container.end(); it++)

#define sz(a) int((a).size())

#define pb push_back

#define sp(c,x) ((c).find(x) != (c).end())  // for set,map

#define vp(c,x) (find(all(c),x) != (c).end())  // for vector

#define uu first

#define vv second

#define fr(i,a,b) for(int i=int(a);i<int(b);++i)

#define nfr(i,a,b) for(int i= int(a);i>=int(b);--i)

#define tc cin>>t ; while(t--)

#define pc()  cout<<"Case "<<cs++<<": "



#define s2(x,y) scanf("%d %d",&x,&y)

#define s2l(x,y) scanf("%lld %lld",&x,&y)

#define s3(x,y,z) scanf("%d %d %d",&x,&y,&z)

#define s3l(x,y,z) scanf("%lld %lld %lld",&x,&y,&z)

#define sc(x)  scanf("%d",&x)

#define sll(x)  scanf("%lld",&x)

#define pfs(x) printf("%d ",x)

#define pfl(x) printf("%d\n",x)

#define el puts("");

#define getcx() getchar()

#define IOS    ios::sync_with_stdio(0); cin.tie(0);cout.tie(0)

#define Fl   freopen("in", "r", stdin);freopen("out","w", stdout)





//============functions

inline bool EQ(double a, double b) { return fabs(a-b) < 1e-9; }

inline bool isLeapYear(ll year) { return (year%400==0) || (year%4==0 && year%100!=0); }

inline void normal(ll &a) { a %= MOD; (a < 0) && (a += MOD); }

inline ll modMul(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); return (a*b)%MOD; }

inline ll modAdd(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); return (a+b)%MOD; }

inline ll modSub(ll a, ll b) { a %= MOD, b %= MOD; normal(a), normal(b); a -= b; normal(a); return a; }

inline ll modPow(ll b, ll p) { ll r = 1; while(p) { if(p&1) r = modMul(r, b); b = modMul(b, b); p >>= 1; } return r; }

inline ll modInverse(ll a) { return modPow(a, MOD-2); }

inline ll modDiv(ll a, ll b) { return modMul(a, modInverse(b)); }

inline bool checkBit(ll n, int i) { return n&(1LL<<i); }

inline ll setBit(ll n, int i) { return n|(1LL<<i);; }

inline ll resetBit(ll n, int i) { return n&(~(1LL<<i)); }



//============ Grid





int dx[]={0,0,1,-1};

int dy[]={1,-1,0,0}; 



void read(){

	

	#ifndef cp		

		Fl;       	

	#endif

}



const ll N=200005;



bool oka[N],okb[N];



void dfs()

{



}

			ll n,m;

bool cmp( ll x)

{

    return x==0 or x==n-1;

}







int main()

{

//		read();

			IOS;

			memset(oka,0,sizeof oka);

			memset(okb,0,sizeof okb);





			ll n,m;

			cin>>n>>m;



			fr(i,0,m)

			{

				ll x,y;

				cin>>x>>y;

				x--,y--;

				if(x==0)

					oka[y]=1;

				if(y==n-1)

					okb[x]=1;



			}



			int k=0;

			for(int i=0;i<n;i++)

				if(oka[i]==1  and okb[i]==1)

				{

					k=1;

					break;

				}



			if(k==0)

				cout<<"IM";



			cout<<"POSSIBLE";

}