#include <bits/stdc++.h>
#pragma GCC optimize ("O2")
#pragma GCC optimize ("unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) {cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;}
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout<<x<<'\n', 0;
const ld eps=1e-7;
const int inf=1000000010;
const ll INF=10000000000000010LL;
const int mod = 1000000007;
const int MAXN = 310, LOG=20;
int n, m, k, u, v, x, y, t, a, b, ans;
int A[MAXN], B[MAXN];
int dp[MAXN*MAXN];
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
cin>>n>>m>>k;
for (int i=1; i<=n; i++){
cin>>A[i];
ans+=A[i];
if (A[i]<k) kill("Impossible")
}
memset(dp, -31, sizeof(dp));
dp[0]=0;
for (int i=1; i<=m; i++){
cin>>B[i];
for (int j=MAXN*MAXN-1; j>=B[i]; j--) dp[j]=max(dp[j], dp[j-B[i]] + min(B[i], n));
}
for (int i=ans; i<MAXN*MAXN; i++) if (dp[i]>=n*k) kill(i-ans)
cout<<"Impossible\n";
return 0;
}
