#pragma GCC optimize ("03")
#include <bitset>
#pragma GCC target ("avx2")
using namespace std;
#include <bits/stdc++.h>
#define rep(i,a,b) for (int i = a; i < b; i++)
#define pb push_back
typedef long long ll;
typedef vector<ll> vi;
int n, m, k;
vector<int> arr, brr;
mt19937 rng(6215);
ll rand(ll maxr) {
return uniform_int_distribution<ll>(0, maxr)(rng);
}
void solve() {
cin >> n >> m >> k;
arr.resize(n);
brr.resize(m);
rep(i,0,n) cin >> arr[i];
rep(i,0,m) cin >> brr[i];
rep(i,0,n) {
if (arr[i] < k) {
cout << "Impossible\n";
return;
}
}
int bsum = 0;
rep(i,0,m) bsum += brr[i];
vector<int> dp(bsum + 1, -1);
dp[0] = 0;
rep(i,0,m) {
for (int j = bsum; j >= 0; j--) {
if (dp[j] == -1) continue;
if (j + brr[i] <= bsum) {
dp[j + brr[i]] = max(dp[j + brr[i]], dp[j] + min(brr[i], n));
}
}
}
int asum = 0;
rep(i,0,n) asum += arr[i];
int ans = -1;
rep(j,asum,bsum+1) {
if (dp[j] >= n * k && dp[j] != 1e9) {
ans = j;
break;
}
}
if (ans == -1) {
cout << "Impossible\n";
}
else {
cout << ans - asum << endl;
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
solve();
}
