#include<bits/stdc++.h>
using namespace std;
const int INF = 1e9;
int n, m, k;
int a[305];
int b[305];
int total = 0;
int totalB = 0;
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m >> k;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
total += a[i];
}
for (int i = 1; i <= m; i++)
{
cin >> b[i];
totalB += b[i];
}
for (int i = 1; i <= n; i++)
{
if (a[i] < k)
{
cout << "Impossible";
return 0;
}
}
int maxx = totalB;
vector<int> dp(maxx + 1, -INF);
dp[0] = 0;
for (int i = 1; i <= m; i++)
{
int real = min(b[i], n);
for (int j = maxx; j >= b[i]; j--)
{
if (dp[j - b[i]] != -INF)
{
dp[j] = max(dp[j], dp[j - b[i]] + real);
}
}
}
int ans = -1;
for (int i = total; i <= maxx; i++)
{
if (dp[i] >= n * k)
{
ans = i - total;
break;
}
}
if (ans == -1)
{
cout << "Impossible";
}
else
{
cout << ans;
}
}
