#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb(x) push_back(x)
#define mp(a, b) make_pair(a, b)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define lscan(x) scanf("%I64d", &x)
#define lprint(x) printf("%I64d", x)
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep2(i, n) for (ll i = (ll)n - 1; i >= 0; i--)
#define REP(i, l, r) for (ll i = l; i < (r); i++)
#define REP2(i, l, r) for (ll i = (ll)r - 1; i >= (l); i--)
#define siz(x) (ll)x.size()
template <class T>
using rque = priority_queue<T, vector<T>, greater<T>>;
const ll mod = 998244353;

template <class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}

template <class T>
bool chmax(T &a, const T &b) {
    if (b > a) {
        a = b;
        return 1;
    }
    return 0;
}

ll gcd(ll a, ll b)
{
	if(a == 0)
		return b;
	if(b == 0)
		return a;
	ll c = a % b;
	while (c != 0)
	{
		a = b;
		b = c;
		c = a % b;
	}
	return b;
}

long long extGCD(long long a, long long b, long long &x, long long &y)
{
	if (b == 0)
	{
		x = 1;
		y = 0;
		return a;
	}
	long long d = extGCD(b, a % b, y, x);
	y -= a / b * x;
	return d;
}

struct UnionFind
{
	vector<ll> data;
	int num;

	UnionFind(int sz)
	{
		data.assign(sz, -1);
		num = sz;
	}

	bool unite(int x, int y)
	{
		x = find(x), y = find(y);
		if (x == y)
			return (false);
		if (data[x] > data[y])
			swap(x, y);
		data[x] += data[y];
		data[y] = x;
		num--;
		return (true);
	}

	int find(int k)
	{
		if (data[k] < 0)
			return (k);
		return (data[k] = find(data[k]));
	}

	ll size(int k)
	{
		return (-data[find(k)]);
	}
};

ll M = 1000000007;

template <int mod>
struct ModInt
{
	int x;

	ModInt() : x(0) {}

	ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

	ModInt &operator+=(const ModInt &p)
	{
		if ((x += p.x) >= mod)
			x -= mod;
		return *this;
	}

	ModInt &operator-=(const ModInt &p)
	{
		if ((x += mod - p.x) >= mod)
			x -= mod;
		return *this;
	}

	ModInt &operator*=(const ModInt &p)
	{
		x = (int)(1LL * x * p.x % mod);
		return *this;
	}

	ModInt &operator/=(const ModInt &p)
	{
		*this *= p.inverse();
		return *this;
	}

	ModInt operator-() const { return ModInt(-x); }

	ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

	ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

	ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

	ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

	bool operator==(const ModInt &p) const { return x == p.x; }

	bool operator!=(const ModInt &p) const { return x != p.x; }

	ModInt inverse() const
	{
		int a = x, b = mod, u = 1, v = 0, t;
		while (b > 0)
		{
			t = a / b;
			swap(a -= t * b, b);
			swap(u -= t * v, v);
		}
		return ModInt(u);
	}

	ModInt pow(int64_t n) const
	{
		ModInt ret(1), mul(x);
		while (n > 0)
		{
			if (n & 1)
				ret *= mul;
			mul *= mul;
			n >>= 1;
		}
		return ret;
	}

	friend ostream &operator<<(ostream &os, const ModInt &p)
	{
		return os << p.x;
	}

	friend istream &operator>>(istream &is, ModInt &a)
	{
		int64_t t;
		is >> t;
		a = ModInt<mod>(t);
		return (is);
	}

	static int get_mod() { return mod; }
};

using mint = ModInt<mod>;

mint mpow(mint x, ll n)
{
	mint ans = 1;
	while (n != 0)
	{
		if (n & 1)
			ans *= x;
		x *= x;
		n = n >> 1;
	}
	return ans;
}

ll mpow2(ll x, ll n, ll mod)
{
	ll ans = 1;
	while (n != 0)
	{
		if (n & 1)
			ans = ans * x % mod;
		x = x * x % mod;
		n = n >> 1;
	}
	return ans;
}

vector<mint> fac;
vector<mint> ifac;

void setcomb(int sz = 2000010)
{
	fac.assign(sz + 1, 0);
	ifac.assign(sz + 1, 0);
	fac[0] = 1;
	for (ll i = 0; i < sz; i++)
	{
		fac[i + 1] = fac[i] * (i + 1); // n!(mod M)
	}
	ifac[sz] = fac[sz].inverse();
	for (ll i = sz; i > 0; i--)
	{
		ifac[i - 1] = ifac[i] * i;
	}
}
mint comb(ll a, ll b)
{
	if(fac.size() == 0)
		setcomb();
	if (a == 0 && b == 0)
		return 1;
	if (a < b || a < 0)
		return 0;
	return ifac[a - b] * ifac[b] * fac[a];
}

mint perm(ll a, ll b)
{
	if(fac.size() == 0)
		setcomb();
	if (a == 0 && b == 0)
		return 1;
	if (a < b || a < 0)
		return 0;
	return fac[a] * ifac[a - b];
}

long long modinv(long long a)
{
	long long b = M, u = 1, v = 0;
	while (b)
	{
		long long t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= M;
	if (u < 0)
		u += M;
	return u;
}

ll modinv2(ll a, ll mod)
{
	ll b = mod, u = 1, v = 0;
	while (b)
	{
		ll t = a / b;
		a -= t * b;
		swap(a, b);
		u -= t * v;
		swap(u, v);
	}
	u %= mod;
	if (u < 0)
		u += mod;
	return u;
}

template <typename Monoid, typename OperatorMonoid = Monoid>
struct LazySegmentTree
{
    using F = function<Monoid(Monoid, Monoid)>;
    using G = function<Monoid(Monoid, OperatorMonoid)>;
    using H = function<OperatorMonoid(OperatorMonoid, OperatorMonoid)>;

    int sz, height;
    vector<Monoid> data;
    vector<OperatorMonoid> lazy;
    const F f;
    const G g;
    const H h;
    const Monoid M1;
    const OperatorMonoid OM0;

    LazySegmentTree(int n, const F f, const G g, const H h,
                    const Monoid &M1, const OperatorMonoid OM0)
        : f(f), g(g), h(h), M1(M1), OM0(OM0)
    {
        sz = 1;
        height = 0;
        while (sz < n)
            sz <<= 1, height++;
        data.assign(2 * sz, M1);
        lazy.assign(2 * sz, OM0);
    }

    void set(int k, const Monoid &x)
    {
        data[k + sz] = x;
    }

    void build()
    {
        for (int k = sz - 1; k > 0; k--)
        {
            data[k] = f(data[2 * k + 0], data[2 * k + 1]);
        }
    }

    inline void propagate(int k)
    {
        if (lazy[k] != OM0)
        {
            lazy[2 * k + 0] = h(lazy[2 * k + 0], lazy[k]);
            lazy[2 * k + 1] = h(lazy[2 * k + 1], lazy[k]);
            data[k] = reflect(k);
            lazy[k] = OM0;
        }
    }

    inline Monoid reflect(int k)
    {
        return lazy[k] == OM0 ? data[k] : g(data[k], lazy[k]);
    }

    inline void recalc(int k)
    {
        while (k >>= 1)
            data[k] = f(reflect(2 * k + 0), reflect(2 * k + 1));
    }

    inline void thrust(int k)
    {
        for (int i = height; i > 0; i--)
            propagate(k >> i);
    }

    void update(int a, int b, const OperatorMonoid &x)
    {
        thrust(a += sz);
        thrust(b += sz - 1);
        for (int l = a, r = b + 1; l < r; l >>= 1, r >>= 1)
        {
            if (l & 1)
                lazy[l] = h(lazy[l], x), ++l;
            if (r & 1)
                --r, lazy[r] = h(lazy[r], x);
        }
        recalc(a);
        recalc(b);
    }

    Monoid query(int a, int b)
    {
        thrust(a += sz);
        thrust(b += sz - 1);
        Monoid L = M1, R = M1;
        for (int l = a, r = b + 1; l < r; l >>= 1, r >>= 1)
        {
            if (l & 1)
                L = f(L, reflect(l++));
            if (r & 1)
                R = f(reflect(--r), R);
        }
        return f(L, R);
    }

    Monoid operator[](const int &k)
    {
        return query(k, k + 1);
    }

    template <typename C>
    int find_subtree(int a, const C &check, Monoid &M, bool type)
    {
        while (a < sz)
        {
            propagate(a);
            Monoid nxt = type ? f(reflect(2 * a + type), M) : f(M, reflect(2 * a + type));
            if (check(nxt))
                a = 2 * a + type;
            else
                M = nxt, a = 2 * a + 1 - type;
        }
        return a - sz;
    }

    template <typename C>
    int find_first(int a, const C &check)
    {
        Monoid L = M1;
        if (a <= 0)
        {
            if (check(f(L, reflect(1))))
                return find_subtree(1, check, L, false);
            return -1;
        }
        thrust(a + sz);
        int b = sz;
        for (a += sz, b += sz; a < b; a >>= 1, b >>= 1)
        {
            if (a & 1)
            {
                Monoid nxt = f(L, reflect(a));
                if (check(nxt))
                    return find_subtree(a, check, L, false);
                L = nxt;
                ++a;
            }
        }
        return -1;
    }

    template <typename C>
    int find_last(int b, const C &check)
    {
        Monoid R = M1;
        if (b >= sz)
        {
            if (check(f(reflect(1), R)))
                return find_subtree(1, check, R, true);
            return -1;
        }
        thrust(b + sz - 1);
        int a = sz;
        for (b += sz; a < b; a >>= 1, b >>= 1)
        {
            if (b & 1)
            {
                Monoid nxt = f(reflect(--b), R);
                if (check(nxt))
                    return find_subtree(b, check, R, true);
                R = nxt;
            }
        }
        return -1;
    }
};

int main(){
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	ll n, s, t, k;
	cin >> n >> s >> t >> k;
	s--, t--;
	ll x[n];
	rep(i, n) cin >> x[i];
	vector<pair<ll, ll>> li[n];
	ll m;
	cin >> m;
	ll a, b, y;
	rep(i, m) cin >> a >> b >> y, li[--a].push_back({--b, y});
	pair<ll, pair<ll, ll>> d[n][k];
	rep(i, n) rep(j, k) d[i][j] = {2e18, {0, 0}};
	rque<pair<ll, pair<pair<ll, ll>, pair<ll, ll>>>> que;
	que.push({x[s], {{s, 0}, {-1, -1}}});
	while(!que.empty()){
		auto q = que.top();
		que.pop();
		ll nd = q.first, now = q.second.first.first, turn = q.second.first.second;
		ll prev = q.second.second.first, pt = q.second.second.second;
		if (chmin(d[now][turn], {nd, {prev, pt}})){
			for(auto &e: li[now]){
				que.push({nd + e.second + x[e.first], {{e.first, min(k - 1, turn + 1)}, {now, turn}}});
			}
		}
	}
	if(d[t][k-1].first > 1e18)
		cout << "Impossible" << endl;
	else{
		cout << "Possible" << '\n' << d[t][k - 1].first << endl;
		vector<ll> ans;
		ans.pb(t + 1);
		ll now = t, nt = k - 1;
		while(d[now][nt].second.first != -1){
			ll prev = d[now][nt].second.first, pt = d[now][nt].second.second;
			ans.pb(prev + 1);
			now = prev, nt = pt;
		}
		cout << ans.size() << endl;
		rep2(i, ans.size()) cout << ans[i] << (i == 0 ? '\n' : ' ');
	}
}