#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 305, MAXH = 90005;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
int n, m, k;
int a[MAXN], b[MAXN];
int diverse = 0, hours = 0;
int max_used = 0;
void read()
{
cin >> n >> m >> k;
int no = 0;
for (int i = 1; i <= n; ++ i)
{
cin >> a[i];
hours += a[i];
if(a[i] < k)no = 1;
}
diverse = k * n;
for (int i = 1; i <= m; ++ i)
{
cin >> b[i];
max_used += b[i];
}
if(no == 1)
{
cout << "Impossible" << endl;
exit(0);
}
}
int dp[MAXN][MAXH/**the number of used hours*/];
void solve()
{
for (int i = 1; i <= m; ++ i)
{
for (int j = 0; j <= max_used; ++ j)
{
//if(dp[i][j] == 0)continue;
dp[i][j] = max(dp[i][j], dp[i-1][j]);
int adding = min(b[i], n);
dp[i][j+b[i]] = max(dp[i][j+b[i]], dp[i-1][j] + adding);
//cout << i << " " << j << " " << dp[i][j] << endl;
}
}
for (int i = 0; i <= max_used; ++ i)
{
if(dp[m][i] >= diverse)
{
cout << i-hours << endl;
return;
}
}
cout << "Impossible" << endl;
}
int main()
{
speed();
read();
solve();
return 0;
}
