#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvl = vector<vll>;
using pll = pair<ll,ll>;
using vpl = vector<pll>;
using vvp = vector<vpl>;
#define f first
#define s second
#define pb push_back
#define all(v) v.begin(), v.end()
int main(){
ios_base::sync_with_stdio(0);cin.tie(NULL);
ll n, m, k, sma=0, smb, mn=1e6;
cin >> n >> m >> k;
for(ll i = 0; i < n; ++i){
ll a;
cin >> a;
mn = min(a, mn);
sma+=a;
}
vll b(m);
for(ll& i:b){cin >> i;smb+=i;}
if(mn<k){
cout << "Impossible";
return 0;
}
vvl dp(m+1, vll(smb+1, -1e9));
dp[0][0]=0;
for(ll i = 1; i <= m; ++i){
for(ll j = 0; j <= smb; ++j){
dp[i][j] = dp[i-1][j];
if(j>=b[i-1])dp[i][j] = max(dp[i][j], dp[i-1][j-b[i-1]]+min(b[i-1],n));
}
}
mn = 1e9;
for(ll j = sma; j <= smb; ++j){
if(dp[m][j]>=n*k){
mn=j;
break;
}
}
if(mn==1e9)cout << "Impossible";
else cout << mn-sma;
}
