//A tree without skin will surely die.
//A man without face is invincible.
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) (x).begin(),(x).end()
#define rep(i,j,k) for (int i=j;i<=k;++i)
#define per(i,j,k) for (int i=j;i>=k;--i)
int const N=1e6+10;
int p[N],q[N],f[N],vis[N],dep[N],cha[N],pre[N],occupy[N],del[N],n,m,idx;
vector<int>a[N],huan[N],b[N],av[N];
inline int find(int x){return (x==f[x])?(x):(f[x]=find(f[x]));}
inline void dfs(int x,int fa){
    vis[x]=1,pre[x]=fa,dep[x]=dep[fa]+1;
    for (auto v:a[x]){
        if (v==fa) continue;
        if (vis[v]){
            if (dep[v]<dep[x]){
                ++idx,++cha[x],--cha[pre[v]];
                int it=x;
                vector<int>s;
                while (1){
                    if (occupy[it]){
                        del[occupy[it]]=del[idx]=1;
                        s.clear();
                        break;
                    }
                    s.push_back(it);
                    occupy[it]=idx;
                    if (it==v) break;
                    it=pre[it];
                }
                it=x;
                while (1){
                    it=find(it);
                    if (dep[it]>dep[v]) f[it]=pre[it];
                    else break;
                }
                huan[idx]=s;
            }
        }else dfs(v,x),b[x].push_back(v);
    }
}
inline void Dfs(int x){
    for (auto v:b[x]) Dfs(v),cha[x]+=cha[v];
}
struct Hash_table{
    int const mod1=998244353;
    int const mod2=1e9+7;
    int const B=1372549;
    int n,hsh1[N],hsh2[N],bse1[N],bse2[N];
    inline void init(vector<int>vec){
        n=vec.size();
        rep(i,1,n) hsh1[i]=(hsh1[i-1]*B%mod1+vec[i-1])%mod1;
        rep(i,1,n) hsh2[i]=(hsh2[i-1]*B%mod2+vec[i-1])%mod2;
        bse1[0]=bse2[0]=1;
        rep(i,1,n) bse1[i]=bse1[i-1]*B%mod1;
        rep(i,1,n) bse2[i]=bse2[i-1]*B%mod2;
    }
    inline pair<int,int> query(int l,int r){
        return make_pair((hsh1[r]+mod1-hsh1[l-1]*bse1[r-l+1]%mod1)%mod1,(hsh2[r]+mod2-hsh2[l-1]*bse2[r-l+1]%mod2)%mod2);
    }
}T1,T2;
inline bool chk(vector<int>v1,vector<int>v2){
    int sz=v1.size();
    vector<int>k;
    for (auto i:v1) k.push_back(i);
    for (auto i:v1) k.push_back(i);
    T1.init(k),T2.init(v2);
    pair<int,int> S=T2.query(1,sz);
    rep(i,1,sz)
        if (T1.query(i,i+sz-1)==S) return 1;
    return 0;
}
int tong[N];
namespace BF{
    vector< vector<int> >huan;
    bool mp[22][22];int u[22],v[22];
    map< vector<int>,int >sz;
    inline void dfs(vector<int>vec){
        if (sz[vec]) return;
        sz[vec]=1;
        for (auto it:huan){
            vector<int>kk=vec;
            int la=vec[it[0]-1];
            rep(k,0,(int)it.size()-2) vec[it[k]-1]=vec[it[k+1]-1];
            vec[it.back()-1]=la;
            dfs(vec);
            vec=kk;
        }
    }
    inline void work(){
        rep(i,1,n) cin>>p[i]>>q[i];
        rep(i,1,m) cin>>u[i]>>v[i];
        rep(i,1,m)
            mp[u[i]][v[i]]=mp[v[i]][u[i]]=1;
        rep(S,1,(1<<n)-1){
            vector<int>V;
            rep(i,1,n)
                if (S>>(i-1)&1) V.push_back(i);
            if (V.size()<=2) continue;
            do{
                if (!mp[V[0]][V.back()]) continue;
                int tag=1;
                rep(i,1,(int)V.size()-1)
                    if (!mp[V[i-1]][V[i]]){tag=0;break;}
                if (!tag) continue;
                // for (auto i:V) cerr<<i<<' ';
                // cerr<<'\n';
                huan.push_back(V);break;
            }while (next_permutation(all(V)));
        }
        vector<int>v1,v2;
        rep(i,1,n) v1.push_back(p[i]),v2.push_back(q[i]);
        dfs(v1);
        // vector<int>k;
        // rep(i,1,n) k.push_back(i);
        // do{
            // if (!sz[k]) continue;
            // for (auto i:k) cout<<i<<' ';
            // cout<<'\n';
        // }while (next_permutation(all(k)));
        if (sz[v2]) cout<<"possible\n";
        else cout<<"impossible\n";
    }
}
void solve(){
    cin>>n>>m;
    if (n<=5) return BF::work();
    rep(i,1,n) cin>>p[i]>>q[i];
    rep(i,1,n) f[i]=i;
    rep(i,1,m){
        int x,y;cin>>x>>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }
    vector<int>roots;
    rep(i,1,n)
        if (!vis[i]) dfs(i,0),roots.push_back(i);
    for (auto i:roots) Dfs(i);
    rep(i,1,n) av[find(i)].push_back(i);
    rep(i,1,n){
        for (auto j:av[i]) ++tong[p[j]];
        for (auto j:av[i]){
            --tong[q[j]];
            if (tong[q[j]]<0) return cout<<"impossible\n",void();
        }
    }
    rep(i,1,n){
        if (cha[i]) continue;
        if (p[i]!=q[i]) return cout<<"impossible\n",void();
    }
    rep(i,1,idx){
        if (del[i]) continue;
        if (!huan[i].size()) continue;
        int tg=0;
        for (auto it:huan[i]) if (cha[it]>1){++tg;break;}
        if (tg) continue;
        // for (auto it:huan[i]) cerr<<it<<' ';
        // cerr<<'\n';
        vector<int>v1,v2;
        for (auto it:huan[i]) v1.push_back(p[it]),v2.push_back(q[it]);
        for (auto it:huan[i]) p[it]=q[it];
        if (!chk(v1,v2)) return cout<<"impossible\n",void();
    }
    cout<<"possible\n";
}
signed main(){
    // freopen("zoo.in","r",stdin);
    // freopen("zoo.out","w",stdout);
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t=1;
    // cin>>t;
    while (t--) solve();
    cerr<<"Time: "<<(double)clock()/CLOCKS_PER_SEC<<" s\n";
    return 0;
}