#include <iostream>
using namespace std;
const int MAXH = 300*305;
long long n, m, k, a[310], b[310], dp[310][MAXH+10], sum;
int main() {
cin >> n >> m >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
if (a[i] < k) {
cout << "Impossible" << endl;
return 0;
}
sum += a[i];
}
for (int i = 1; i <= m; i++) cin >> b[i];
for (int i = 0; i <= m; i++) for (int j = 0; j <= MAXH; j++) dp[i][j] = -1e18;
dp[0][0] = 0;
for (int i = 1; i <= m; i++) {
for (int j = 0; j <= MAXH; j++) {
dp[i][j] = dp[i-1][j];
if (j >= b[i]) dp[i][j] = max(dp[i][j],dp[i-1][j-b[i]]+min(n,b[i]));
}
}
for (int i = sum; i <= MAXH; i++) {
if (dp[m][i] >= n*k) {
cout << i-sum << endl;
return 0;
}
}
cout << "Impossible" << endl;
}
