// dfmt off
T lread(T=long)(){return readln.chomp.to!T;}T[] lreads(T=long)(long n){return iota(n).map!((_)=>lread!T).array;}
T[] aryread(T=long)(){return readln.split.to!(T[]);}void arywrite(T)(T a){a.map!text.join(' ').writeln;}
void scan(L...)(ref L A){auto l=readln.split;foreach(i,T;L){A[i]=l[i].to!T;}}alias sread=()=>readln.chomp();
void dprint(L...)(lazy L A){debug{auto l=new string[](L.length);static foreach(i,a;A)l[i]=a.text;arywrite(l);}}
static immutable MOD=10^^9+7;alias PQueue(T,alias l="b<a")=BinaryHeap!(Array!T,l);import std;
// dfmt on

void main()
{
    long N, M;
    scan(N, M);
    auto G = new long[][](N);
    foreach (_; 0 .. M)
    {
        long a, b;
        scan(a, b);
        a--, b--;
        G[a] ~= b;
        G[b] ~= a;
    }
    bool dfs(long v, long d)
    {
        if (v == N - 1 && d == 2)
            return true;
        if (2 <= d)
            return false;
        bool ans;
        foreach (w; G[v])
            ans = ans || memoize!dfs(w, d + 1);
        return ans;
    }

    writeln(dfs(0, 0) ? "POSSIBLE" : "IMPOSSIBLE");
}
