dist = [[False] * 100] * 100

N = int(input())
L = []
S = []
ans = 0

for i in range(N):
    ls = input().split()
    L.append(int(ls[0]))
    S.append(int(ls[1]) - 1)
    dist[i][S[i]] = True
    dist[i][i] = True
    ans += L[i]

for k in range(N):
    for i in range(N):
        for j in range(N):
            dist[i][j] |= (dist[i][k] & dist[k][j])

for i in range(N):
    flag = True
    for j in range(i):
        if dist[i][j] and dist[j][i]:
            flag = False

    if not flag:
        continue

    for j in range(N):
        if dist[i][j] and not dist[j][i]:
            flag = False

    if not flag:
        continue

    mincost = 999
    for j in range(i, N):
        if dist[i][j] and dist[j][i]:
            mincost = min(mincost, L[j])

    ans += mincost

print(ans / 2)