#include <iostream>
#include <stdio.h>
#include <vector>
#include <queue>
#define llint long long
#define inf 1e18

using namespace std;

struct edge{
	llint to, cap, rev;
	edge(llint a, llint b, llint c){
		to = a, cap = b, rev = c;
	}
};

llint n;
llint a[40], b[40];

vector<edge> G[80];
int S, T;
llint level[80], iter[80];

void bfs(llint s)
{
	for(int i = 1; i <= T; i++) level[i] = inf;
	level[s] = 0;
	
	queue<int> Q;
	Q.push(s);
	while(Q.size()){
		int v = Q.front();
		Q.pop();
		for(int i = 0; i < G[v].size(); i++){
			int u = G[v][i].to;
			if(G[v][i].cap <= 0 || level[u] < inf) continue;
			level[u] = level[v] + 1;
			Q.push(u);
		}
	}
}

llint dfs(int v, llint f)
{
	if(v == T) return f;
	
	llint ret;
	for(int i = iter[v]; i < G[v].size(); i++){
		if(level[v] >= level[G[v][i].to] || G[v][i].cap <= 0) continue;
		ret = dfs(G[v][i].to, min(f, G[v][i].cap));
		if(ret > 0){
			G[v][i].cap -= ret;
			G[G[v][i].to][G[v][i].rev].cap += ret;
			return ret;
		}
	}
	return 0;
}

void add_edge(int s, int t, llint cap)
{
	G[s].push_back(edge(t, cap, G[t].size()));
	G[t].push_back(edge(s, 0, G[s].size()-1));
}

int main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n;
	for(int i = 2; i <= n; i++) cin >> a[i] >> b[i];
	
	llint asum = 0, bsum = 0;
	for(int i = n; i >= 2; i--) asum += a[i], bsum += b[i];
	if(asum > bsum){
		swap(asum, bsum);
		for(int i = 2; i <= n; i++) swap(a[i], b[i]);
	}
	
	S = 2*n+1, T = 2*n+2;
	for(int i = 2; i <= n; i++) add_edge(S, i, a[i]);
	for(int i = 2; i <= n; i++) add_edge(n+i, T, b[i]);
	for(int i = 2; i <= n; i++){
		for(int j = 2; j <= n; j++){
			if(i == j) continue;
			add_edge(i, j, 1);
		}
	}
	
	llint ans = 0, flow;
	while(1){
		bfs(S);
		if(level[T] >= inf) break;
		for(int i = 1; i <= T; i++) iter[i] = 0;
		while(1){
			flow = dfs(S, inf);
			if(flow <= 0) break;
			ans += flow;
		}
	}
	cout << asum - ans + 1 << endl;
	
	return 0;
}