#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
const int maxn = 303;
int n, m, k, a[maxn], b[maxn];
int m1, m2, b1[maxn], b2[maxn], mv1, mv2;
int dp1[maxn][maxn*maxn], dp2[maxn][maxn*maxn], wtf[maxn*maxn];
void solve() {
cin >> n >> m >> k;
for(int i = 1; i <= n; i++) {
cin >> a[i];
}
for(int i = 1; i <= m; i++) {
cin >> b[i];
}
int sma = 0;
for(int i = 1; i <= n; i++) {
sma+= a[i];
if(a[i] < k) {
cout << "Impossible" << endl;
return;
}
}
int smb = 0;
for(int i = 1; i <= m; i++) {
smb+= b[i];
if(b[i] <= n) {
b1[++m1] = b[i];
mv1+= b[i];
}
else {
b2[++m2] = b[i];
mv2+= b[i];
}
}
if(m < k || smb < sma) {
cout << "Impossible" << endl;
return;
}
dp1[0][0] = 1;
for(int i = 1; i <= m1; i++) {
for(int j = 0; j <= mv1; j++) {
dp1[i][j] = dp1[i-1][j];
if(j-b1[i] >= 0) dp1[i][j]|= dp1[i-1][j-b1[i]];
}
}
dp2[0][0] = 0;
for(int i = 1; i <= mv2; i++) dp2[0][i] = -inf;
for(int i = 1; i <= m2; i++) {
for(int j = 0; j <= mv2; j++) {
dp2[i][j] = dp2[i-1][j];
if(j-b2[i] >= 0) dp2[i][j] = max(dp2[i][j],dp2[i-1][j-b2[i]]+1);
}
}
int ans = inf;
// for(int i = 0; i <= mv1; i++) {
// if(dp1[m1][i] == 0) continue;
// for(int j = 0; j <= mv2; j++) {
// if(j >= sma-i && dp2[m2][j]*n >= n*k-i) {
// ans = min(ans, i+j-sma);
// }
// }
// }
for(int i = 0; i <= mv1; i++) {
wtf[i] = inf;
}
int r = mv2+1;
int cur = inf;
for(int i = 0; i <= mv1; i++) {
while(i+r-1 >= sma && r-1 >= 0) {
r--;
if(dp2[m2][r] < 0) continue;
if(n*k - dp2[m2][r]*n <= i) cur = min(cur,r);
else wtf[n*k - dp2[m2][r]*n] = min(wtf[n*k - dp2[m2][r]*n],r);
}
cur = min(cur,wtf[i]);
if(dp1[m1][i] == 1) ans = min(ans, i+cur-sma);
}
if(ans > smb-sma) cout << "Impossible" << endl;
else cout << ans << endl;
}
int32_t main() {
ios::sync_with_stdio(false); cin.tie(0);
// freopen("in.in", "r", stdin);
// freopen("out.out", "w", stdout);
int tt = 1;
// cin >> tt;
while(tt--) {
solve();
}
}
