#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const int MAX_V = 100;
const int INF = 10000000;

struct Edge {
    int to, cap, rev;  //行き先、容量、逆辺
    Edge(int to, int cap, int rev) : to(to), cap(cap), rev(rev) {}
};

vector<Edge> G[MAX_V];
int level[MAX_V];
int iter[MAX_V];

void add_edge(int from, int to, int cap) {
    G[from].push_back(Edge(to, cap, G[to].size()));
    G[to].push_back(Edge(from, 0, G[from].size() - 1));
}

void bfs(int s) {
    memset(level, -1, sizeof(level));
    queue<int> que;
    level[s] = 0;
    que.push(s);
    while (!que.empty()) {
        int v = que.front();
        que.pop();
        for (int i = 0; i < G[v].size(); i++) {
            Edge& e = G[v][i];
            if (e.cap > 0 && level[e.to] < 0) {
                level[e.to] = level[v] + 1;
                que.push(e.to);
            }
        }
    }
}

int dfs(int v, int t, int f) {
    if (v == t) return f;
    for (int& i = iter[v]; i < G[v].size(); i++) {
        Edge& e = G[v][i];
        if (e.cap > 0 && level[v] < level[e.to]) {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0) {
                e.cap -= d;
                G[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}

int max_flow(int s, int t) {
    int flow = 0;
    while (true) {
        bfs(s);
        if (level[t] < 0) return flow;
        memset(iter, 0, sizeof(iter));
        int f;
        while ((f = dfs(s, t, INF)) > 0) {
            flow += f;
        }
    }
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        add_edge(0, i, a);
        add_edge(i + n - 1, 2 * n - 1, b);
    }

    for (int i = 1; i < n; i++) {
        for (int j = 1; j < n; j++) {
            if (i == j) continue;
            add_edge(i, j + n - 1, INF);
        }
    }

    cout << max_flow(0, 2 * n - 1) + 1 << "\n";
    return 0;
}