#include <bits/stdc++.h>
using namespace std;
#define fileio() freopen("input.txt","r",stdin); freopen("output.txt","w",stdout)
#define fio() ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define all(x) (x).begin(), (x).end()
#define cmprs(x) sort(all(x)),x.erase(unique(all(x)),x.end())
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define sz(a) (int)(a.size())
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int dx[] = {1,-1,0,0,1,1,-1,-1};
const int dy[] = {0,0,1,-1,1,-1,1,-1};
const ll MOD = 1e9+7;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3f;
const int MAX = 303;
int N,M,K,A[MAX],B[MAX];
int dp[MAX][MAX*MAX];
// int go(int i, int x) {
// if (i==0) return (x==0?0:-INF);
// int &ret=dp[i][x];
// if (ret!=-1) return ret;
// ret=go(i-1,B[i]);
// if (x-B[i]>=0) ret=max(ret, go(i-1,x-B[i])+min(N,B[i]));
// return ret;
// }
int main() {
fio();
// memset(dp,-1,sizeof dp);
cin>>N>>M>>K;
int suma=0, sumb=0;
for (int i=1; i<=N; i++) cin>>A[i], suma+=A[i];
for (int i=1; i<=M; i++) cin>>B[i], sumb+=B[i];
for (int i=1; i<=N; i++) {
if (A[i]<K) {
cout<<"Impossible\n";
return 0;
}
}
dp[0][0]=0;
for (int i=1; i<=M; i++) {
for (int x=0; x<MAX*MAX; x++) {
dp[i][x]=dp[i-1][x];
if (x-B[i]>=0) dp[i][x]=max(dp[i][x], dp[i-1][x-B[i]]+min(N,B[i]));
}
}
for (int i=suma; i<=sumb; i++) {
if (dp[M][i]>=N*K) {
cout<<i-suma<<'\n';
return 0;
}
}
cout<<"Impossible\n";
return 0;
}
