MUAQUA

#include <bits/stdc++.h>
using namespace std;

using ll = long long;
using pi32 = pair<int, int>;
using pi64 = pair<int64_t, int64_t>;

const int maxN = 1e5 + 5;
const ll INF = 1e18 + 7;
const int MOD = 998244353;

int n, m;
ll a[maxN], b[maxN];

priority_queue<ll> d;

void solve() {
    ll sum = 0;
    for (int i = 1; i <= n; ++i)
        sum += b[i];

    for (int i = 1; i <= n; ++i)
        d.push(b[i] - a[i]);

    while (m--) {
        sum -= d.top(); d.pop();
    }

    ll ans = sum;
    while (!d.empty()) {
        sum -= d.top(); d.pop();
        ans = min(ans, sum);
    }

    cout << ans << '\n';
}

int main() {
#ifdef LOCAL
    freopen("in1.txt", "r", stdin);
#else
    freopen("MUAQUA.inp", "r", stdin);
    freopen("MUAQUA.out", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> m;
    for (int i = 1; i <= n; ++i)
        cin >> a[i];
    for (int i = 1; i <= n; ++i)
        cin >> b[i];

    solve();

    return 0;
}