C :

#include<stdio.h>
int main()
 {
 	int n,i,sum,big;
 	sum=0;
 	big=0;
 	scanf("%d",&n);
 	int a[n],b[n],c[n];
 	for(i=0;i<n;i++)
 	scanf("%d",&a[i]);
 	for(i=0;i<n;i++)
 	scanf("%d",&b[i]);
 	for(i=0;i<n;i++)
 	{
 		if(a[i]>=b[i])
 		sum+=a[i];
 		else sum+=b[i];
	 }
	 for(i=0;i<n;i++)
	 {
 		if(a[i]>=b[i])
 		c[i]=b[i];
 		else c[i]=a[i];
 		
 		if(c[i]>big)
 		big=c[i];
 		
	 }
	 sum+=big;
	 printf("%d",sum);
  } 

C++ :

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e6+10;
typedef pair<int,int> PII;
typedef long long ll;
typedef priority_queue<int , vector<int>, greater<int>> minqueue;  //′óD?μ?′ó queue
typedef priority_queue<int, vector<int>, less<int>> maxqueue;      //′ó′óμ?D? queue

int gcd(int a, int b){  //×?′ó1?òòêy 
    return b ? gcd(b, a % b) : a;
}

int lcm(int a, int b){ //×?D?1?±?êy 
    return a * b / __gcd(a, b);
}

int qmi(int base, int power, int p)  //?ì?ù?Y?óóà 
{
	int result = 1;   
	while (power > 0)           
	{
		if (power & 1)         							
			result = result * base % p;   
		base = base * base % p ;       						
		power >>= 1;         						
	}
	return result % p;       
}

int a[5][100010];

void solve()
{
	int n;
	cin>>n;
	for(int i=1;i<=2;i++){
		for(int j=1;j<=n;j++){
			cin>>a[i][j];
		}
	}
	int mx=-1e9;
	int sum1=0,sum2=0;
	int k=0;
	int mn=-1e9;
	for(int i=1;i<=n;i++){
		mn=max(mn,min(a[1][i],a[2][i]));
	}
	int ans=0;
	for(int i=1;i<=n;i++){
		ans+=max(a[1][i],a[2][i]);
	}
	ans+=mn;
	cout<<ans<<'\n';
}

signed main()
{
	ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	int t;
	t=1;
	//cin>>t; 
	while(t--)     
	{
		solve();
	}
	return 0;
}