#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <stdio.h>
using namespace std;
#define int long long
int MOD = 1000000007;
signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N;
	cin >> N;
	vector<int> A(N - 1);
	vector<int> B(N - 1);
	int res = 0;
	int sumA = 0;
	int sumB = 0;
	for (int i = 0; i < N - 1; i++) {
		cin >> A[i] >> B[i];
	}
	for (int t = 0; t < 100; t++) {
		for (int i = 0; i < N - 1; i++) {
			int sum = 0;
			for (int j = 0; j < N - 1; j++) {
				if (i != j) {
					sum += B[j];
				}
			}
			if (sum < A[i]) {
				A[i] = sum;
			}
		}
		swap(A, B);
	}




	for (int i = 0; i < N - 1; i++) {
		sumA += A[i];
		sumB += B[i];
	}
	cout << min(sumA, sumB) + 1 << endl;
}