#include <bits/stdc++.h>
using namespace std;
#define ll long long
// #define int ll
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define REP1(i, n) FOR(i, 1, n+1)
#define RREP(i, n) for (int i = (n)-1; i >= 0; i--)
#define RREP1(i, n) for (int i = (n); i >= 1; i--)
#define pii pair<int, int>
#define ppi pair<pii, int>
#define pip pair<int, pii>
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) (int)((x).size())
#define f first
#define s second
#define pb push_back
#define endl '\n'
#define IOS() ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
const ll maxn = 305;
const ll mod = 1e9+7;
const ll inf = 1ll<<60;
ll mpw(ll a, ll p, ll m = mod){
ll ret = 1;
while(p > 0){
if (p & 1){
ret *= a;
ret %= m;
}
p >>= 1;
a *= a;
a %= m;
}
return ret;
}
ll inv(ll a){
return mpw(a, mod-2);
}
int n, m, k;
int dp[maxn][maxn*maxn];
signed main(){
IOS();
cin>>n>>m>>k;
int tot = 0;
REP(i, n){
int tt; cin>>tt;
tot += tt;
if (tt < k){
cout<<"Impossible"<<endl;
return 0;
}
}
REP1(i, m){
int b; cin>>b;
REP(j, maxn*maxn){
dp[i][j] = dp[i-1][j];
if (j >= b) dp[i][j] = max(dp[i][j], dp[i-1][j-b] + min(b, n));
}
}
int ret = -1;
FOR(i, tot, maxn*maxn){
if (dp[m][i] >= n*k){
ret = i;
break;
}
}
if (ret == -1) cout<<"Impossible"<<endl;
else {
cout<<ret-tot<<endl;
}
}
