#include <bits/stdc++.h>
//#pragma GCC optimize("O3")
//#pragma GCC optimize("unroll-loops")
using namespace std;
#define int long long
#define vi vector<int>
#define vl vector<long long>
#define vii vector<pair<int,int>>
#define vll vector<pair<long long,long long>>
#define pb push_back
#define ll long long
#define ld long double
#define nl '\n'
#define boost ios::sync_with_stdio(false)
#define mp make_pair
#define se second
#define fi first
#define fore(i, y) for(int i = 0; i < y; i++)
#define forr(i,x,y) for(int i = x;i<=y;i++)
#define forn(i,y,x) for(int i = y; i >= x; i--)
#define all(v) v.begin(),v.end()
#define sz(v) (int)v.size()
#define clr(v,k) memset(v,k,sizeof(v))
#define rall(v) v.rbegin() , v.rend()
#define pii pair<int,int>
#define pll pair<ll , ll>
const ll MOD = 1e9 + 7;
const ll INF = 1e18 + 1;
ll gcd(ll a , ll b) {return b ? gcd(b , a % b) : a ;} // greatest common divisor (gcd)
ll lcm(ll a , ll b) {return a * (b / gcd(a , b));} // least common multiple (lcm)
// HERE IS THE SOLUTION
signed main()
{
boost;
cin.tie(0);
cout.tie(0);
int n , m , k;
cin>>n>>m>>k;
vi a(n) , b(m);
int sb = 0 , sa = 0;
fore(i , n)
{
cin>>a[i];
if(a[i] < k)
{
cout<<"Impossible"<<nl;
return 0;
}
sa+=a[i];
}
fore(i , m)
{
cin>>b[i];
sb+=b[i];
}
int s = sb - sa;
if(s < 0)
{
cout<<"Impossible"<<nl;
return 0;
}
int dp[sb + 1] , reach[sb + 1];
fore(i , sb + 1)
{
dp[i] = -INF;
reach[i] = 0;
}
dp[0] = 0;
reach[0] = 1;
for(auto x : b)
{
forn(j , sb , 0)
{
if(j + x <= sb && reach[j])
{
reach[j + x] = 1;
dp[j + x] = max(dp[j + x] , dp[j] + min(n , x));
}
}
}
int ans = -1;
fore(i , sb + 1)
{
if(dp[i] >= n*k && i >= sa)
{
ans = i;
break;
}
}
if(ans != -1)
cout<<ans - sa<<nl;
else
cout<<"Impossible"<<nl;
}
