#include<bits/stdc++.h>
using namespace std;
const int nx = 305, inf = 1e9;
int n,m,k,total,totalA,a[nx],b[nx],dp[nx][nx*nx];
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>m>>k;
for(int i = 1; i <= n; i++) cin>>a[i], totalA+=a[i];
for(int i = 1; i <= m; i++) cin>>b[i], total+=b[i];
for(int i = 0; i <= m; i++) for(int j = 1; j <= total; j++) dp[i][j]=-inf;
for(int i = 1; i <= m; i++)
{
for(int j = 1; j <= total; j++)
{
dp[i][j]=dp[i-1][j];
if(b[i]<=j) dp[i][j]=max(dp[i][j],dp[i-1][j-b[i]]+min(b[i],n));
}
}
for(int i = 1; i <= n; i++)
{
if(a[i] < k) return cout<<"Impossible", 0;
}
int res = -1;
for(int i = totalA; i <= total; i++)
{
if(dp[m][i] >= n*k)
{
res = i-totalA;
break;
}
}
if(res==-1) cout<<"Impossible";
else cout<<res;
}
