#include<bits/stdc++.h>
#define int long long
using namespace std;
inline int read(){
    int x=0,f=1;char c=getchar();
    while(c<'0'||'9'<c){if(c=='-')f=-1;c=getchar();}
    while('0'<=c&&c<='9'){x=(x<<1)+(x<<3)+c-'0';c=getchar();}
    return x*f;
}
const int N=1e6+2;
int n,maxa=1,ans,m,c[N];
struct qwq{
    int l,r;
}tmp[N],d[N];
vector<int>v;
inline int getid(int x){
    return lower_bound(v.begin(),v.end(),x)-v.begin()+1;
}
signed main(){
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);
    n=read();
    for(int i=1,a,b;i<=n;i++){
        a=read(),b=read();
        if(a<b)maxa=max(maxa,b);
        else maxa=max(maxa,a),tmp[++m]={a,b},v.push_back(a),v.push_back(b-1);
    }
    sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
    for(int i=1;i<=m;i++)c[getid(tmp[i].l)]++,c[getid(tmp[i].r-1)]--;
    m=0;int sum=0,l=0;
    for(int i=v.size();i>=1;i--){
        sum+=c[i];
        if(sum)l=l?l:v[i-1];
        else if(l)d[++m]={l,v[i-1]+1},l=0;
    }
    sum=maxa;
    for(int i=1;i<=m;i++)sum+=((d[i].l-d[i].r)<<1);
    ans=sum;
    for(int i=1;i<=m;i++)sum-=((d[i].l-d[i].r)<<1),ans=min(ans,sum+maxa-d[i].r);
    printf("%lld",ans);
    return 0;
}