#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<Int> cs(n),ds(n);
  for(Int i=0;i<n;i++) cin>>cs[i]>>ds[i];
  Int ans=0;
  for(Int i=0;i<n;i++){
    ans+=cs[i];
    ans+=ds[i];
  }
  const Int INF = 1e18;
  vector<Int> dp(n+1,INF);
  dp[0]=0;
  Int res=INF,val=INF;
  for(Int i=0;i<n;i++){
    chmin(res,dp[i]-ds[i]);
    chmin(val,res+cs[i]);
    chmin(dp[i+1],val);
  }
  ans+=*min_element(dp.begin()+1,dp.end());
  cout<<ans<<endl;
  return 0;
}