#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MAXN (305)
ll N,M,K,totalA;
ll A[MAXN], B[MAXN];
ll dp[MAXN * MAXN];
int main() {
ios_base::sync_with_stdio(false);cin.tie(0);
cin>>N>>M>>K;
bool ok = 1;
for(ll i = 0;i < N;i++){ //number of dishes
cin>>A[i];
totalA += A[i];
if(A[i] < K) ok = 0;
}
for(ll i = 0;i < M;i++){ //number of chefs
cin>>B[i];
}
if(!ok){
cout<<"Impossible"<<'\n';
return 0;
}
for(ll i = 0;i < MAXN * MAXN;i++){
dp[i] = -1e18;
}
dp[0] = 0;
for(ll i = 0;i < M;i++){
for(ll j = MAXN * MAXN - 1;j >= B[i];j--){
dp[j] = max(dp[j],dp[j - B[i]] + min(B[i],N));
}
}
ll minimum = 1e18;
for(ll i = totalA;i < MAXN * MAXN;i++){
if(dp[i] >= N * K){
minimum = i;
break;
}
}
if(minimum == 1e18) cout<<"Impossible"<<'\n';
else cout<<minimum - totalA<<'\n';
}
