import numpy as np
from scipy.sparse.csgraph import maximum_flow
from scipy.sparse import csr_matrix
from itertools import product

def solve(ab):
    INF = 10**9
    ab = [(INF,INF)]+ab
    n = len(ab)

    g = np.zeros((2*n+2,2*n+2), dtype=int)

    # 0: start, 1: goal, 2-(n+1): left, (n+2)-(2n-1): right

    for i,(a,b) in enumerate(ab):
        g[0,i+2] = a
        g[i+n+2,1] = b
    for i,j in product(range(n), repeat=2):
        if i == j:
            continue
        g[i+2,j+n+2] = INF

    t = maximum_flow(csr_matrix(g), 0, 1).flow_value

    ta = sum(a for a,b in ab[1:])
    tb = sum(b for a,b in ab[1:])

    return t-max(ta,tb)+1


n = int(input())
ab = [tuple(map(int,input().split())) for _ in range(n-1)]
print(solve(ab))