#include<bits/stdc++.h>
#define poly vector<int>
#define IOS ios::sync_with_stdio(false)
#define ll long long
#define mp make_pair
#define mt make_tuple
#define pa pair < int,int >
#define fi first
#define se second
#define inf 1e18
#define mod 998244353
#define sz(x) ((int)((x).size()))
#define int ll
// #define N 
using namespace std;
const int N=400005;
int n,m,a[N],b[N];
int dfn[N],low[N],fa[N],DFN;
poly G[N],g[N];
unordered_map<int,int>Mp[N];
int kmp[N<<1];
int siz[N];
inline int gf(int x)
{
    while (x!=fa[x]) x=fa[x]=fa[fa[x]];
    return x;
}
void tarjan(int k,int fa)
{
    dfn[k]=++DFN;
    low[k]=DFN;
    for (auto u:G[k])
    {
        if (u==fa) continue;
        if (!dfn[u])
        {
            tarjan(u,k);
            low[k]=min(low[k],low[u]);
            if (low[u]>dfn[k])
            {
                Mp[max(u,k)][min(u,k)]=1;
            }
        } else low[k]=min(low[k],dfn[u]);
    }
}
int exist_even;
int sta[N],tp;
int id[N];
void tarjan1(int k,int fa)
{
    dfn[k]=++DFN;
    low[k]=DFN;
    sta[++tp]=k;
    for (auto u:G[k])
    {
        if (u==fa) continue;
        if (gf(u)!=gf(k)) continue;
        if (!dfn[u])
        {
            tarjan1(u,k);
            low[k]=min(low[k],low[u]);
            if (low[u]>=dfn[k])
            {
                poly g;
                int nn=0,mm=0;
                g.push_back(k);
                while (1)
                {
                    int v=sta[tp];
                    tp--;
                    g.push_back(v);
                    if (v==u) break;
                }
                nn=sz(g);
                for (int j=0;j<sz(g);j++) id[g[j]]=j+1;
                for (int j=1;j<sz(g);j++)
                    for (auto v:G[g[j]])
                    {
                        if (id[v]&&id[v]<j+1) mm++;
                    }
                for (int j=0;j<sz(g);j++) id[g[j]]=0;
                if (nn%2==0&&nn>2) exist_even=1;
                if (nn%2==1&&mm>nn) exist_even=1;
            }
        } else low[k]=min(low[k],dfn[u]);
    }
}
inline int work(poly y,poly x)
{
    int n=sz(x),m=sz(y);
    for (int i=2,j=0;i<=n;i++)
    {
        while (j&&x[j]!=x[i-1]) j=kmp[j];
        if (x[j]==x[i-1]) j++;
        kmp[i]=j;
    }
    for (int i=1,j=0;i<=m;i++)
    {
        while (j&&x[j]!=y[i-1]) j=kmp[j];
        if (x[j]==y[i-1]) j++;
        if (j==n) return 1;
    }
    return 0;
}
inline int calc(poly g)
{
    poly gg=g;
    sort(gg.begin(),gg.end());
    for (int i=0;i<sz(g);i++) g[i]=lower_bound(gg.begin(),gg.end(),g[i])-gg.begin();
    poly vis(sz(g),0);
    int res=0;
    for (int i=0;i<sz(g);i++)
        if (!vis[i])
        {
            int now=i;
            while (!vis[now])
            {
                vis[now]=1;
                now=g[now];
            }
            res^=1;
        }
    return res;
}
void BellaKira()
{
    cin>>n>>m;
    for (int i=1;i<=n;i++) cin>>a[i]>>b[i];
    for (int i=1;i<=m;i++)
    {
        int x,y;
        cin>>x>>y;
        G[x].push_back(y);
        G[y].push_back(x);
    }
    for (int i=1;i<=n;i++)
        if (!dfn[i]) tarjan(i,0);
    for (int i=1;i<=n;i++)
        fa[i]=i,siz[i]=0;
    for (int k=1;k<=n;k++)
        for (auto u:G[k])
            if (k<u)
            {
                if (Mp[u].count(k)) continue;
                if (gf(u)==gf(k)) siz[gf(k)]++;
                else siz[gf(k)]+=siz[gf(u)]+1,fa[gf(u)]=fa[gf(k)];
            }
    for (int i=1;i<=n;i++)
        g[gf(i)].push_back(i);
    for (int i=1;i<=n;i++) dfn[i]=low[i]=0;
    for (int i=1;i<=n;i++)
        if (gf(i)==i)
        {
            if (siz[i]>sz(g[i]))
            {
                exist_even=0;
                for (auto u:g[i])
                    if (!dfn[u]) 
                    {
                        tarjan1(u,0);
                        tp=0;
                    }
                poly x,y;
                for (auto u:g[i]) x.push_back(a[u]);
                for (auto u:g[i]) y.push_back(b[u]);
                sort(x.begin(),x.end());
                sort(y.begin(),y.end());
                if (x!=y) 
                {
                    cout<<"impossible\n";
                    return;
                }
                for (int j=1;j<sz(x);j++)
                    if (x[j-1]==x[j]) exist_even=1;
                if (!exist_even)
                {
                    poly x,y;
                    for (auto u:g[i]) x.push_back(a[u]);
                    for (auto u:g[i]) y.push_back(b[u]);
                    if (calc(x)!=calc(y))
                    {
                        cout<<"impossible\n";
                        return;
                    }
                }
            }
            else
            {
                int now=i;
                poly nw;nw.push_back(i);
                while (sz(nw)<sz(g[i]))
                {
                    for (auto u:G[now])
                        if (gf(u)==i&&(nw.size()==1||nw[sz(nw)-2]!=u))
                        {
                            now=u;
                            nw.push_back(now);
                            break;
                        }
                }
                poly x,y;
                for (auto u:nw) x.push_back(a[u]);
                for (auto u:nw) x.push_back(a[u]);
                for (auto u:nw) y.push_back(b[u]);
                if (!work(x,y)) 
                {
                    cout<<"impossible\n";
                    return;
                }
            }
        }
    cout<<"possible\n";
}
signed main()
{
    IOS;
    cin.tie(0);
    int T=1;
    while (T--)
    {
        BellaKira();
    }
}
/*list:
1.mod 998244353 or 1e9+7 or ???
2.N
3.duipai shuju xingtai duoyidian
...
*/