#include<bits/stdc++.h>
#define pb push_back
#define mp make_pair
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<'\n'
#define dout(a) cout<<a<<' '<<#a<<'\n'
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<'\n'
#define yn(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
const int leg = 1e9 + 7;
const int mod = 998244353;
using namespace std;
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
//ifstream cin(".in");
//ofstream cout(".out");
in3(n,m,k);
vin(a,n);
vin(b,m);
bool ok = 1;
f0r(i, n){
if(a[i] < k)ok = 0;
}
if(!ok)out("Impossible");
else{
int sum = accumulate(all(b), 0LL);
vvi dp(m+1, vi(sum + 1, -1)); // can we form the sum j with elements in small?
dp[0][0] = 0;
FOR(i, 1, m+1){
FOR(j, 0, sum+1){
if(b[i-1] <= j && dp[i-1][j - b[i-1]] != -1)dp[i][j] = max(dp[i][j], dp[i-1][j - b[i-1]] + min(n, b[i-1]));
dp[i][j] = max(dp[i][j], dp[i-1][j]);
}
}
// vout(dp[m]);
// out(dp[2][6]);
int sa = accumulate(all(a), 0LL);
int ans = -1;
for(int i = sa; i<sum+1; i++){
if(dp[m][i] >= n * k){
ans = i;
break;
}
}
if(ans != -1)out(ans - sa);
else out("Impossible");
}
}
