#include<bits/stdc++.h>
using namespace std;
#define int int64_t
#define pb push_back
#define st first
#define nd second
#define pii pair<int, int>
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
int dp[90009];
int32_t main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
for(int i=0;i<=300*300;i++) dp[i] = -1e18;
dp[0] = 0;
int n, m, k;
cin >> n >> m >> k;
int sum = 0;
for(int i=0;i<n;i++) {
int x;
cin >> x;
if(x<k) {
cout << "Impossible\n";
return 0;
}
sum+=x;
}
for(int i=0;i<m;i++) {
int x;
cin >> x;
for(int j=300*300;j>=0;j--) {
if(j+x<=300*300) {
dp[j+x] = max(dp[j+x], dp[j]+min(n, x));
}
}
}
for(int i=sum;i<=300*300;i++) {
if(dp[i]>=n*k) {
cout << i-sum << "\n";
return 0;
}
}
cout << "Impossible\n";
}
