#include <bits/stdc++.h>
using namespace std;
#define erorp(x) cout<<#x<<"={"<<(x.F)<<" , "<<x.S<<"}"<<endl
#define print(v,r) f(i,0,r) cout<<v[i]<<" "; cout<<endl
#define eror(x) cout<<#x<<'='<<(x)<<endl
#define f_(i,a,b) for(int i=a;i>=b;i--)
#define f(i,a,b) for(int i=a;i<b;i++)
#define nb(x) __builtin_popcount(x)
#define maxm(a,b) a=max(a,b)
#define minm(a,b) a=min(a,b)
#define Add(x,y) x=(x+y)%mod
#define lst(x) x[x.size()-1]
#define sz(x) int(x.size())
#define mp make_pair
#define ll long long
#define pb push_back
#define S second
#define F first
const int N=330;
int n,m,k,sum,dp[N*N];
int main(){
cin>>n>>m>>k;
f(i,0,n){
int x;
cin>>x;
sum+=x;
if(x<k) return cout<<"Impossible",0;
}
dp[0]=0;
f(i,1,N*N) dp[i]=-N*N;
f(i,0,m){
int x;
cin>>x;
f_(i,N*N-1,0){
if(i-x>=0){
maxm(dp[i],dp[i-x]+min(n,x));
}
}
}
f(i,sum,N*N){
if(dp[i]>=n*k){
return cout<<i-sum,0;
}
}
cout<<"Impossible";
}
