#include<iostream>
#include<cstring>
#include<vector>
#include<algorithm>
#include<cmath>
#include<queue> 
#define ll long long
using namespace std;
int n;
struct nod{int a,b;}lis[2010];
bool cmp(nod x,nod y){return x.a<y.a;}
int ans=0x3f3f3f3f;
void f(int x,int t,int aL,int bL){
	int p=min(aL,bL);
	t+=p,aL-=p,bL-=p;
	if(t+aL+bL>ans) return;
	
	if(x==n+1){
		ans=t+aL+bL;
		return;
	}
	
	if(!aL&&!bL){
		f(x+1,t,lis[x].a,0);
		f(x+1,t,0,lis[x].b);
		if(x!=n){
			f(x+2,t,lis[x].a,lis[x+1].b);
			f(x+2,t,lis[x+1].a,lis[x].b);
		}
	}else if(!aL&&bL){
		f(x+1,t,lis[x].a,bL);
		f(x,t+bL,0,0);
	}else if(aL&&!bL){
		f(x+1,t,aL,lis[x].b);
		f(x,t+aL,0,0);
	}
}
int main(){
    freopen("task.in","r",stdin);
    freopen("task.out","w",stdout);
    
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d%d",&lis[i].a,&lis[i].b);
    sort(lis+1,lis+1+n,cmp);
    f(1,0,0,0);
    cout<<ans;
    
    return 0;
}