#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define pb push_back
#define ar array
#define all(x) x.begin(), x.end()
#define siz(x) (int)x.size()
#define FOR(x, y, z) for(int x = (y); x < (z); x++)
#define ROF(x, z, y) for(int x = (y-1); x >= (z); x--)
#define F0R(x, z) FOR(x, 0, z)
#define R0F(x, z) ROF(x, 0, z)
#define trav(x, y) for(auto&x:y)
using ll = long long;
using vi = vector<int>;
using vl = vector<long long>;
using pii = pair<int, int>;
using vpii = vector<pair<int, int>>;
template<class T> inline bool ckmin(T&a, T b) {return b < a ? a = b, 1 : 0;}
template<class T> inline bool ckmax(T&a, T b) {return b > a ? a = b, 1 : 0;}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const char nl = '\n';
const int mxN = 305;
const int MOD = 1e9 + 7;
const long long infLL = 1e18;
int n, m, k;
int a[mxN], b[mxN];
int dp[mxN*mxN];
void no(){
cout << "Impossible\n";
exit(0);
}
int32_t main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> m >> k;
F0R(i, n) cin >> a[i];
F0R(i, m) cin >> b[i];
if(*min_element(a, a+n)<k) no();
F0R(i, mxN*mxN) dp[i] = -MOD;
dp[0] = 0;
F0R(i, m){
R0F(j, mxN*mxN-b[i]){
ckmax(dp[j+b[i]], dp[j]+min(n, b[i]));
}
}
FOR(i, accumulate(a, a+n, 0), mxN*mxN){
if(dp[i] >= n*k){
cout << i-accumulate(a, a+n, 0) << nl;
return 0;
}
}
no();
return 0;
}
