#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<long long, long long>
#define pb push_back
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
const ll N = 305;
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ll block = 450;
ll n,m,k,sA = 0, sB = 0, sMn = 0;
ll a[N], b[N], dp[N][N * N];
void to_thic_cau(){
cin >> n >> m >> k;
for(int i = 1; i <= n;i++){
cin >> a[i];
sA += a[i];
}
for(int i = 1; i <= m;i++){
cin >> b[i];
sB += b[i]; sMn += min(b[i], n);
}
for(int i = 1; i <= n;i++) if(a[i] < k){cout << "Impossible" << '\n'; return;}
if(sB < sA){
cout << "Impossible" << '\n';
return;
}
if(sMn < n * k){
cout << "Impossible" << '\n';
return;
}
for(int i = 1; i <= m;i++){
for(int j = 0; j <= sB;j++){
dp[i][j] = dp[i-1][j];
if(j >= b[i]) dp[i][j] = max(dp[i][j], dp[i - 1][j - b[i]] + min(n, b[i]));
}
}
for(int j = sA; j <= sB;j++){
if(dp[m][j] >= n * k){
cout << j - sA << '\n';
return;
}
}
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
ll tc = 1;
//cin >> tc;
while(tc--) to_thic_cau();
}
