/* ID: Sho10 LANG: C++ */ #include <bits/stdc++.h> //Andrei Alexandru a.k.a Sho10 #define ll long long int #pragma GCC optimize("O3") #pragma GCC optimize("Ofast") #define all(a) (a).begin(), (a).end() #define sz size #define f first #define s second #define pb push_back #define er erase #define in insert #define mp make_pair #define pi pair #define rc(s) return cout<<s,0 #define endl '\n' #define mod 1000000007 #define PI 3.14159265359 #define CODE_START ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0); using namespace std; ll n,m,a[400005],b[400005]; int32_t main(){ CODE_START; cin>>n>>m; for(ll i=0;i<n+m-1;i++) cin>>a[i]; for(ll i=0;i<n+m-1;i++) { cin>>b[i]; } ll sum=0; ll ans=0; ll l=(n+m-1)/2,r=(n+m-1)/2; for(ll i=0;i<n+m-1;i++) { if(l==r){ sum=sum+b[l]; }else { sum=sum+b[l]+b[r]; } if(sum<a[i]){ ans=ans+sum; sum=0; }else { ans=ans+a[i]; } } cout<<ans<<endl; }