#pragma GCC optimize("Ofast")
#include"bits/stdc++.h"
#define int long long
using namespace std;
const int sz = 1e3 + 3;
int a[sz], b[sz];
int dp[sz * sz];
signed main() {
cin.tie(nullptr)->sync_with_stdio(false);
int n, m, k;
cin >> n >> m >> k;
int sm = 0;
bool f = false;
for (int i = 1; i <= n; i ++) {
cin >> a[i];
sm += a[i];
if (a[i] < k) {
f = true;
}
}
for (int i = 1; i <= m; i ++) {
cin >> b[i];
}
if (f) {
cout << "IMPOSSIBLE";
return 0;
}
int S = accumulate(b + 1, b + 1 + m, (int)0)+1;
int T = accumulate(a + 1, a + 1 + n, (int)0);
int dp[S];
for (int j=0; j<=S; j++) {
dp[j] = -1;
}
dp[0] = 0;
for (int i=1; i<=m; i++) {
int val = b[i];
for (int j=S; j>=val; j--) {
if (dp[j-val]!=-1) {
dp[j] = max(dp[j],dp[j-val]+min(n,val));
}
}
}
int ans = -1;
for (int i=T; i<=S; i++) {
//cout << i <<" " << dp[i] << endl;
if (dp[i]>=n*k) {
ans=i-T;
break;
}
}
if (ans==-1) {
cout << "Impossible" << endl;
}
else {
cout << ans << endl;
}
}
