#include <iostream>
using namespace std;
const int maxN = 305, inf = 1e9;
int barr[maxN], dp[maxN][maxN*maxN];
int main(){
int n, m, k;
cin >> n >> m >> k;
int total = 0;
for (int i = 0; i < n; i++){
int a;
cin >> a;
if (a < k){
cout << "Impossible" << endl;
return 0;
}
total += a;
}
for (int i = 0; i < m; i++) cin >> barr[i];
for (int i = 0; i < m; i++){
for (int j = 0; j < maxN*maxN; j++) dp[i][j] = -inf;
}
dp[0][barr[0]] = min(n, barr[0]);
for (int i = 1; i < m; i++){
for (int j = 0; j < maxN*maxN; j++){
dp[i][j] = dp[i-1][j];
if (barr[i] <= j){
dp[i][j] = max(dp[i][j], dp[i-1][j-barr[i]] + min(n, barr[i]));
}
}
}
bool pos = 0;
int ans;
for (int i = total; i < maxN*maxN; i++){
if (dp[m-1][i] >= n*k){
pos = 1;
ans = i;
break;
}
}
if (!pos) cout << "Impossible" << endl;
else cout << ans-total << endl;
}
