#include <bits/stdc++.h>
using namespace std;
#define int long long
#define fi first
#define se second
#define pii pair <int, int>
const int mn = 305, mm = (1 << 20) + 1, inf = 1e18;
int a[mn], f[mn], m, n, k, b[mn];
int dp[mn][mn * mn];
void solve(){
cin >> n >> m >> k;
int sum = 0, sum1 = 0, min_val = INT_MAX;
for(int i = 1; i <= n; i++){
cin >> a[i];
sum += a[i];
min_val = min(min_val, a[i]);
}
for(int i = 1; i <= m; i++){
cin >> b[i];
sum1 += b[i];
}
if(m < k || min_val < k || sum1 < sum){
cout << "Impossible\n";
return;
}
// cout << 1 << '\n';
fill(&dp[0][0], &dp[0][0] + mn * mn * mn, -inf);
dp[0][0] = 0;
for(int i = 1; i <= m; i++){
for(int j = 0; j <= sum1; 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]));
}
}
}
int res = INT_MAX;
for(int j = max(sum, n * k); j <= sum1; j++){
if(dp[m][j] >= n * k){
res = j;
break;
}
}
if(res == INT_MAX) cout << "Impossible\n";
else cout << res - sum;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t = 1;
// cin >> t;
while(t--) solve();
}
