#include <bits/stdc++.h>
#include <algorithm>
#include <functional>
#include <map>
#include <queue>
#include <set>
#include <stack>
using namespace std;
using ll = long long;
using ull = unsigned long long;
#define REP(i, m, n) for (ll(i) = (ll)(m); i < (ll)(n); ++i)
#define REP2(i, m, n) for (ll(i) = (ll)(n)-1; i >= (ll)(m); --i)
#define rep(i, n) REP(i, 0, n)
#define rep2(i, n) REP2(i, 0, n)
#define all(hoge) (hoge).begin(), (hoge).end()
#define en '\n'
using Edge = pair<int, long long>;
using Graph = vector<vector<Edge>>;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef vector<vector<vector<ll>>> vvvl;
typedef vector<string> vs;
typedef vector<vector<string>> vvs;
typedef pair<ll, ll> P;
constexpr long long INF = 1LL << 60;
constexpr int INF_INT = 1 << 25;
// constexpr long long MOD = (ll)1e9 + 7;
// constexpr long long MOD = 998244353LL;
using ld = long double;
static const ld pi = 3.141592653589793L;
template <class T> inline void print(T x) { cout << x << '\n'; }
template <class T> bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T> bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}

long long gcd(long long x, long long y) { return y ? gcd(y, x % y) : x; }
//素因数分解
vector<pair<long long, long long>> prime_factorize(long long N) {
    vector<pair<long long, long long>> res;
    for (long long a = 2; a * a <= N; ++a) {
        if (N % a != 0) continue;
        long long ex = 0;
        while (N % a == 0) {
            ++ex;
            N /= a;
        }
        res.push_back({a, ex});
    }
    if (N != 1) res.push_back({N, 1});
    return res;
}
//素数判定
bool is_prime(long long x) {
    if (x <= 1) return false;
    for (long long i = 2; i * i <= x; i++)
        if (x % i == 0) return false;
    return true;
}

// modint: mod 計算を int を扱うように扱える構造体
template <int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator-() const noexcept { return val ? MOD - val : 0; }
    constexpr Fp operator+(const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator-(const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator*(const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator/(const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator+=(const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator-=(const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator*=(const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator/=(const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator==(const Fp& r) const noexcept { return this->val == r.val; }
    constexpr bool operator!=(const Fp& r) const noexcept { return this->val != r.val; }
    friend constexpr ostream& operator<<(ostream& os, const Fp<MOD>& x) noexcept { return os << x.val; }
    friend constexpr Fp<MOD> modpow(const Fp<MOD>& a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};

const int MOD = 1000000007;
using mint = Fp<MOD>;

// 愚直計算による二項係数計算
mint comb(long long n, long long r) {
    mint res = 1;
    for (long long i = 0; i < r; ++i) {
        res *= (n - i);
        res /= (i + 1);
    }
    return res;
}
// ~~~~~~~~~~~~~~memo~~~~~~~~~~~~~~
// for (int i = 0; i < n; ++i)
// int型の2次元配列(h×w要素の)の宣言
// vector<vector<int>> data(h, vector<int>(w));
// rotate(s.begin(), s.begin() + 1, s.end());
// sort(all(a),greater<int>());
// s.substr(0,2) 先頭から2文字切り出す
// for (auto it = mp.rbegin();it != mp.rend(); ++it)
// vector<vector<vector<int>>> dp(n + 1, vector<vector<int>>(w + 1, vector<int>(k+1, 0)));
const ll MX = 200010;
bool f1[MX],fN[MX];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll n,m;
    cin >> n >> m;
    rep(i,m) {
        ll a,b;
        cin >> a >> b;
        if (a == 1) f1[b] = true;
        if (b == n) fN[a] = true;
    }
    REP(i,1,n+1){
        if (f1[i] && fN[i]) {
            print("POSSIBLE");
            return 0;
        }
    }
    print("IMPOSSIBLE");
    
    return 0;
}


Measured memory_bytes: 3872