#include <bits/stdc++.h>
#define F first
#define S second
#define all(x) x.begin(),x.end()
#define endl '\n'

using namespace std;

using ll = long long;
using pii = pair<int, int>;
const int INF = 0x3f3f3f3f;
const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;
const int MOD = 1000000007;
const int dx[] = { 0, 0, -1, 1, 1, -1,  1, -1};
const int dy[] = {-1, 1,  0, 0, 1, -1, -1,  1};


ll AP(ll a, ll b){
  return ((a+b)*(b-a+1))/2;
}
const int MAXN = 200010;
int a[MAXN], b[MAXN];
int n, m;
ll f(ll x){
  ll sum = 0;
  for(int i=0; i<n; i++){
    ll t = (a[i]-x)/b[i];
    if(x <= a[i])
      sum += (t+1);
  }
  return sum;
}

int main() {
  ios_base::sync_with_stdio(false); cin.tie(NULL);

  cin >> n >> m;

  for(int i=0; i<n; i++){
    cin >> a[i];
  }
  for(int i=0; i<n; i++){
    cin >> b[i];
  }
  ll lo=2, hi=1e9, mn=1;
  while(lo<=hi){
    ll mid = (lo+hi)/2;
    if(f(mid) >= m){
      mn = mid;
      lo = mid+1;
    }else{
      hi = mid-1;
    }
  }

  ll sum = 0;
  for(int i=0; i<n; i++){
    ll t = (a[i]-mn)/b[i];
    if(mn <= a[i]){
      sum += a[i]*(t+1) - b[i]*AP(0, t);
    }
  }
  ll get = f(mn);
  if(mn == 1){
    get += m;
    sum += m;
  }
  if(get >= m){
    sum -= (get-m)*mn;
  }
  cout << sum << endl;
  return 0;
}