#include <bits/stdc++.h>
using namespace std;
#define el "\n"
typedef long long ll;
const int MM = 1e5+5, MOD = 1e9+7;
int N, M, K, wst = 1e9, sum, dp[MM];
int main() {
cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false);
cin >> N >> M >> K;
for(int i = 1, x; i <= N; i++) cin >> x, wst = min(wst, x), sum += x;
if(wst < K) { cout << "Impossible" << el; return 0; }
for(int i = 1, x, s = 0; i <= M; i++) {
cin >> x; s += x;
for(int j = s; j >= 0; j--) {
dp[j+x] = max(dp[j+x], dp[j] + min(x, N)); }
} for(int i = sum; i < MM; i++) if(dp[i] >= N*K) { cout << i - sum << el; return 0; }
cout << "Impossible" << el;
}
