#include<bits/stdc++.h>
using namespace std;
int a1[300001],b1[300001],ans,n,asum,bsum;
int main(){
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a1[i];
        asum+=a1[i];
    }
    for(int i=0;i<n;i++){
        cin>>b1[i];
        bsum+=b1[i];
    }
    ans=ceil((float)(asum+bsum)/2);
    cout<<ans;
    return 0;
}