#include<bits/stdc++.h>
using namespace std;
using lli = long long;
const lli maxN =3e2 + 5;
lli f[maxN * maxN],g[maxN * maxN];
lli a[maxN],b[maxN],n,sum,m,k;
void input()
{
cin >> n >> m >> k;
sum = 0;
for (lli i = 1;i <= n;++i)
{
cin >> a[i];
sum += a[i];
}
for (lli i = 1;i <= m;++i) cin >> b[i];
for (lli j = 1;j < maxN * maxN;++j) g[j] = -1e18;
g[0] = 0;
}
void solve()
{
for (lli i = 1;i <= n;++i) if (a[i] < k) {cout << "Impossible";return;}
for (lli i = 1;i <= m;++i)
{
for (lli j = 0;j < maxN * maxN;++j)
{
f[j] = -1e18;
if (j - b[i] >= 0 && g[j - b[i]] != -1e18) f[j] = g[j - b[i]] + min(b[i],n);
f[j] = max(g[j],f[j]);
//if (j == 10 && i == 4) cout << g[j] << " " << f[j] << "\n";
}
for (lli j = 0;j < maxN * maxN;++j)
{
g[j] = f[j];
}
//if (i == 1) cout << f[3] << "\n";
}
lli ans = 1e18;
for (lli j = 1;j < maxN * maxN;++j)
{
if (j - sum >= 0 && f[j] >= n * k) ans = min(ans,j - sum);
}
if (ans == 1e18) cout << "Impossible";
else cout << ans;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
// freopen("G.inp","r",stdin);
// freopen("G.out","w",stdout);
input();
solve();
}
/*
4 4 1
1 2 3 4
2 3 4 2
*/
