Ataque Programado

#include <bits/stdc++.h>
using namespace std;
#define SZ(a) (int)a.size()

int main() {
    int n, m, s;
    while(cin >> n >> m >> s and (n + m + s)) {
        vector<vector<int>> G(n);
        vector<int> refem(n), num_of_sol(n), g(n);
        for(int i = 0; i < n; i++)
            cin >> num_of_sol[i];
        for(int i = 0; i < n; i++)
            cin >> refem[i];
        while(m--) {
            int u, v;
            cin >> u >> v; u--; v--;
            g[v]++;
            G[u].push_back(v);
        }
        priority_queue<pair<int, int>> pq;
        for(int i = 0; i < n; i++)
            if(!g[i])
                pq.push({-num_of_sol[i], i});
        int qtd = 0;
        while(!pq.empty()) {
            int v = pq.top().second;
            // nao da pra atacar o que tem menos soldados
            if(s <= -pq.top().first)
                break;
            pq.pop();
            qtd++;
            s += refem[v];
            for(int u : G[v])
                if(--g[u] == 0)
                    pq.push({-num_of_sol[u], u});
        }
        cout << (qtd == n ? "possivel" : "impossivel") << '\n';
    }

    return 0;
}