#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

#define MAX 110000
#define int long long

int per[MAX], siz[MAX];

void init(int n){
  for(int i = 0; i < n; i++){
    per[i] = i;
    siz[i] = 1;
  }
}

int find(int x){

  if(x == per[x]) return x;
  else return per[x] = find(per[x]);
}

void unite(int x, int y){
  x = find(x);
  y = find(y);

  if(x == y) return;

  if(siz[x] > siz[y]){
    siz[x] += siz[y];
    per[y] = x;
  } else {
    siz[y] += siz[x];
    per[x] = y;
  }
}

bool same(int x, int y){
  return find(x) == find(y);
}


int kruskal(vector<pair<int,pair<int,int> > > &edge){
  int res = 0;
  
  sort(edge.begin(), edge.end());

  for(int i = 0; i < edge.size(); i++){
    if(same(edge[i].second.first, edge[i].second.second)) continue;

    unite(edge[i].second.first, edge[i].second.second);

    res += edge[i].first;
  }

  return res;
}

signed main(){

  int N, sum = 0;
  int C, D;
  vector<pair<int,pair<int,int> > > edge;

  cin>>N;

  for(int i = 1; i <= N; i++){
    cin>>C>>D;
    sum += C;
    edge.push_back(make_pair(C ,make_pair(0,i)));
    if(i != 1) edge.push_back(make_pair(D ,make_pair(i-1,i)));
  }

  init(N+2);
  
  cout<<sum + kruskal(edge)<<endl;
  
  return 0;
}