#include <iostream>
#include <vector>
#include <algorithm>
#include <bitset>
using namespace std;
using ll = long long;
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#define MAX(a, b) (((a) < (b)) ? (b) : (a))
int const nmax = 300;
int const inf = 1000000000;
int v[5 + nmax], v2[5 + nmax];
bitset<5 + nmax * nmax> dpinit, dp[5 + nmax];
int dist[5 + nmax * nmax];
int main()
{
int n, k, m;
cin >> n >> m >> k;
int sum = 0;
for(int i = 1;i <= n; i++) {
cin >> v[i];
sum += v[i];
if(v[i] < k) {
cout << "Impossible";
return 0;
}
}
dpinit[0] = 1;
int ptr = 0;
dp[0][0] = 1;
for(int i = 1;i <= m; i++) {
cin >> v2[i];
if(v2[i] < n)
dpinit |= (dpinit<<v2[i]);
else{
for(int j = ptr; 0 <= j; j--)
dp[j + 1] |= (dp[j]<<v2[i]);
++ptr;
}
}
dist[n * nmax + 1] = inf;
for(int i = n * nmax; 0 <= i; i--){
if(dpinit[i] == 1)
dist[i] = 0;
else
dist[i] = dist[i + 1] + 1;
}
int result = inf;
for(int i = 0; i <= ptr; i++){
for(int j = 0; j <= i * nmax; j++){
if(dp[i][j] == 1){
int diff = MAX(n * k - i * n, sum - j);
if(diff <= 0)
result = MIN(result, j - sum);
else
result = MIN(result, dist[diff] + diff + j - sum);
}
}
}
if(1 + nmax * nmax <= result)
cout << "Impossible";
else
cout << result;
return 0;
}
