#include <bits/stdc++.h>
using namespace std;
int N, M, K;
int totA;
int A[310], B[310];
int dp[310][310*310];
int f(int m, int t) {
if (m==0) {
if (t==0) return 0;
else return -1e9;
}
int& res = dp[m][t];
if (res != -1) return res;
res = max(f(m-1,t), f(m-1,t-B[m])+min(N,B[m]));
// cout << m << " " << t << " " << res << endl;
return res;
}
int main() {
cin >> N >> M >> K;
for(int i=1; i<=N; i++) {
cin >> A[i];
totA += A[i];
if (A[i] < K) {
cout << "Impossible" << endl;
return 0;
}
}
for(int i=1; i<=M; i++) {
cin >> B[i];
}
memset(dp, -1, sizeof(dp));
for(int i=totA; i<=300*300; i++) {
// cout << i << " " << f(N,i) << endl;
if (f(M, i) >= N*K) {
cout << i-totA << endl;
return 0;
}
}
cout << "Impossible" << endl;
}
