// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <unordered_map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
using namespace std;
#define int long long
#define endl "\n"
#define fi first
#define se second
const int M=1e9+7;
const int inf = 1e14;
const int LOG=18;
const int N=5e1+5;
int n , m , c , w , k , t=1 , q=1 , x , y , z , l , r;
void solve(){
cin >> n >> m;
vector<int>a(n),b(n);
for (int i=0;i<n;i++){
cin >> a[i];
}
for (int i=0;i<n;i++){
cin >> b[i];
}
priority_queue<pair<int,int>>pq;
vector<int>cn(n),vl(n);
for (int i=0;i<n;i++){
pq.push({0,i});
}
int c=0;
while (c<n*m and pq.size()){
auto h=pq.top();
pq.pop();
int i=h.se;
if (cn[i]<m){
vl[i]+=max(a[i],b[i]);
cn[i]++;
}
else{
vl[i]+=b[i];
}
pq.push({-vl[i],i});
c++;
}
cout << *min_element(vl.begin(),vl.end()) << endl;
}
signed main()
{
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);//DO NOT USE IN INTERACTIVE
cout << fixed << setprecision(9);
srand(time(0));
// int t=1;
// cin >> t;
for (int _=1;_<=t;_++){
solve();
q++;
}
}
