#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll (i) = 0; (i) < (n); (i)++)
#define rep1(i, n) for(ll (i) = 1; (i) <= (n); (i)++)
#define rrep(i, n) for(ll (i) = (n) - 1; (i) >= 0; (i)--)
#define rrep1(i, n) for(ll (i) = (n); (i) >= 1; (i)--)
const ll INF = 1145141919;
const ll MOD = 1000000007;
template<class T> void chmax(T &a, const T &b){if(a < b){a = b;}}
template<class T> void chmin(T &a, const T &b){if(a > b){a = b;}}
template<class T> bool find_from_set(set<T> &S, const T &t){
    return S.find(t) != S.end();
}
typedef pair<ll, P> LP;

int main(){

    ll N;
	cin >> N;
	vector<ll>A(N), B(N);
	rep(i, N)cin >> A[i] >> B[i];
	priority_queue<LP, vector<LP>, greater<LP> >Q;
	set<P>S;
	Q.push(LP(A[0] * 2, P(1, A[0])));
	while(!Q.empty()){
		ll cst = Q.top().first;
		P p = Q.top().second;
		Q.pop();
		if(find_from_set(S, p))continue;
		S.insert(p);
		ll idx = p.first, mum = p.second;
		if(idx == N){
			cout << cst << endl;
			break;
		}
		Q.push(LP(cst + A[idx] * 2, P(idx + 1, A[idx])));
		cst += A[idx] + B[idx];
		if(mum > A[idx]){
			cst -= mum;
			cst += A[idx];			
		}
		Q.push(LP(cst, P(idx + 1, min(A[idx], mum))));		
	}

    return 0;
}