#include <bits/stdc++.h>
using namespace std;
const int MAXN = 305, INF = 1e9;
int a[MAXN], b[MAXN], dp[MAXN][MAXN*MAXN];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n,m,k; cin>>n>>m>>k;
int sa = 0;
for(int i = 1; i <= n; i++){
cin>>a[i];
sa += a[i];
}
int sb = 0;
for(int i = 1; i <= m; i++){
cin>>b[i];
sb += b[i];
}
for(int i = 1; i <= n; i++)
if(a[i] < k){
cout<<"Impossible\n";
return 0;
}
for(int j = 1; j <= sb; j++) dp[0][j] = -INF;
for(int i = 1; i <= m; i++)
for(int j = 1; j <= sb; j++){
dp[i][j] = dp[i-1][j];
if(j >= b[i])dp[i][j] = max(dp[i-1][j], dp[i-1][j - b[i]] + min(b[i],n));
}
for(int j = sa; j <= sb; j++)
if(dp[m][j] >= n*k){
cout<<j-sa<<"\n";
return 0;
}
cout<<"Impossible\n";
}
