vY7prw - Online C++ Compiler & Debugging Tool

#include <bits/stdc++.h>
using namespace std;
#define Bismillah ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define ll long long
void SemogaBisa() {
    ll n, m;
    cin >> n >> m;
    vector<ll> a(n), b(m);
    ll suma = 0, sumb = 0;

    for(ll i = 0; i < n; i++) { cin >> a[i]; suma += a[i]; }
    for(ll i = 0; i < m; i++) { cin >> b[i]; sumb += b[i]; }
    sort(b.begin(), b.end(), greater<ll>());

    ll ans = 0, p = 0;
    while(m != 0) {
        if ((suma + ans)* m > (sumb - ans)* n) break;
            ll sum = 1, s = p; {
            while (b[s] == b[s+1]) { sum++; s++; }
            ans += sum * b[p];
            p += sum;
            m -= sum;
            n += sum;
        }
    }
    cout << (m != 0 ? ans : -1) << endl;
}
int main() {
	Bismillah;
	SemogaBisa();
	return 0;
}