Untitled

def min_subsidies():
    n = int(input().strip())
    a, b = [], []

    for _ in range(n):
        ai, bi = map(int, input().strip().split())
        a.append(ai)
        b.append(bi)
    
    net = [0] * n
    
    for i in range(n):
        net[i] -= b[i]
        net[a[i] - 1] += b[i]

    total_subsidy = sum(-balance for balance in net if balance < 0)

    print(total_subsidy)

min_subsidies()