// g++-15 1.cpp -std=c++20 -O2 -I .
#include <bits/stdc++.h>
using namespace std;

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;

#include <atcoder/modint>
using namespace atcoder;

using ll = long long;
using ld = long double;
 
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vld = vector<ld>;
using vvld = vector<vld>;
using vst = vector<string>;
using vvst = vector<vst>;

#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define pq_big(T) priority_queue<T,vector<T>,less<T>>
#define pq_small(T) priority_queue<T,vector<T>,greater<T>>
#define all(a) a.begin(),a.end()
#define rep(i,start,end) for(ll i=(start);i<(ll)(end);i++)
#define per(i,start,end) for(ll i=(start);i>=(ll)(end);i--)
#define uniq(a) sort(all(a));a.erase(unique(all(a)),a.end())

random_device seed;
mt19937_64 randint(seed());

ll grr(ll mi, ll ma) { // [mi, ma)
    return mi + randint() % (ma - mi);
}

int main(){
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  int n;cin>>n;
  ll a=0,b=0;
  ll px=-1,py=-1;
  rep(i,0,n){
    ll x,y;cin>>x>>y;
    ll na=0,nb=0;
    
    if(y==px){
      na=max(na,a+y);
    }
    else{
      na=max(na,a);
    }
    if(y==py){
      na=max(na,b+y);
    }
    else{
      na=max(na,b);
    }

    if(x==px){
      nb=max(nb,a+x);
    }
    else{
      nb=max(nb,a);
    }
    if(x==py){
      nb=max(nb,b+x);
    }
    else{
      nb=max(nb,b);
    }

    if(x==y){
      na+=x;
      nb+=x;
    }

    a=na;b=nb;
    px=x;py=y;

    // cout<<a<<" "<<b<<endl;
  }
  cout<<max(a,b)<<endl;
}