#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for (int i = a; i <= (int)b; i++)
#define FORD(i, a, b) for (int i = a; i >= (int)b; i--)
#define ll long long
#define pb push_back
#define fi first
#define se second
#define all(a) a.begin(), a.end()
#define sz(a) (int)a.size()
#define MASK(a) (1LL<<(a))
#define BIT(mask, a) ((mask >> (a))&1)
template <class A, class B> bool minimize (A &a, const B b) {if (a > b) {a = b;return true;} return false;}
template <class A, class B> bool maximize (A &a, const B b) {if (a < b) {a = b;return true;} return false;}
const int MAXN = 300 + 5;
int n, m, k;
int a[MAXN], b[MAXN];
int dp[MAXN][MAXN * MAXN];
void init (void) {
cin >> n >> m >> k;
FOR(i, 1, n) cin >> a[i];
FOR(i, 1, m) cin >> b[i];
}
void process (void) {
if (m < k || *min_element(a + 1, a + 1 + n) < k) {
cout << "Impossible";
return;
}
int allTime = 0;
FOR(i, 1, n) allTime+= a[i];
int allTimeB = 0;
FOR(i, 1, m) allTimeB+= b[i];
memset(dp, - 0x3f, sizeof dp);
dp[0][0] = 0;
FOR(i, 1, m) FOR(j, 0, allTimeB) {
maximize (dp[i][j], dp[i - 1][j]);
if (j >= b[i]) {
maximize (dp[i][j], dp[i - 1][j - b[i]] + min(b[i], n));
}
}
int ans = 2e9;
FOR(j, allTime, allTimeB) if (dp[m][j] >= n * k) {
ans = min (ans, j - allTime);
}
if (ans >= 2e9) {
cout << "Impossible";
} else {
cout << ans;
}
}
int main (void) {
ios_base::sync_with_stdio(0); cin.tie(0);
#define kieuoanh "boi19_kitchen"
if (fopen(kieuoanh".inp", "r")) {
freopen(kieuoanh".inp", "r", stdin); freopen(kieuoanh".out", "w", stdout);
}
init();
process();
return 0;
}
