#include <bits/stdc++.h>
using namespace std;
const int N = 333;
int n, m, k, sm, cc, ans = INT_MAX, a[N], b[N], dp[N][N * N];
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> m >> k;
for(int i = 1;i<=n;i++) cin >> a[i], sm += a[i], cc |= (a[i] < k);
for(int i = 1;i<=m;i++) cin >> b[i];
if(cc) return cout << "Impossible", 0;
for(int i = 0;i<N;i++) for(int j = 0;j<N*N;j++) dp[i][j] = INT_MIN;
dp[0][0] = 0;
for(int i = 1;i<=m;i++){
for(int j = 0;j + b[i]<N*N;j++){
dp[i][j + b[i]] = max(dp[i - 1][j + b[i]], dp[i - 1][j] + min(n, b[i]));
if(dp[i][j + b[i]] >= n * k && j + b[i] >= sm) ans = min(ans, j + b[i] - sm);
}
}
if(ans == INT_MAX) cout << "Impossible";
else cout << ans;
}
