#include <bits/stdc++.h>
#define int long long

using namespace std;

inline int read () {
    int w = 1, s = 0; char ch = getchar ();
    for (; ! isdigit (ch); ch = getchar ()) if (ch == '-') w = -1;
    for (; isdigit (ch); ch = getchar ()) s = (s << 1) + (s << 3) + (ch ^ 48);
    return s * w;
}

void solve () {
	int n = read (), k = read ();
    
    vector <int> a (n), b (n);
    for (int i = 0; i < n; i ++) {
        a[i] = read ();
    }
    for (int i = 0; i < n; i ++) {
        b[i] = read ();
    }

    sort (a.begin (), a.end ());
    sort (b.begin (), b.end ());

    vector <int> c (n);
    for (int i = 0; i < n; i ++) {
        c[i] = a[i] - b[i];
    }
    sort (c.begin (), c.end (), greater ());

    int ans = 0;
    for (int i = 0, j = 0; i < n && j < k; i ++, j ++) {
        if (c[i] < 0) {
            break;
        }
        ans += c[i];
    }

    printf ("%lld\n", ans);
} 

signed main () {
	// ios::sync_with_stdio (false);
    // cin.tie (nullptr);
    
	int T = 1; 
	// cin >> T;
	// T = read ();

	while (T --) {
		solve ();
	}
	
	return 0;
}