def SCC_Tarjan(g):
    n = len(g)
    order = [-1]*n # 負なら未処理、[0,n) ならpre-order, n ならvisited
    low = [0]*n
    ord_now = 0
    parent = [-1]*n
    gp = [0]*n
    gp_num = 0
    S = []
    q = []
    for i in range(n):
        if order[i] == -1:
            q.append(i)
            while q:
                v = q.pop()
                if v >= 0:
                    if order[v] != -1: continue
                    order[v] = low[v] = ord_now
                    ord_now += 1
                    S.append(v)
                    q.append(~v)
                    for c in g[v]:
                        if order[c] == -1: 
                            q.append(c)
                            parent[c] = v
                        else:
                            low[v] = min(low[v], order[c])
                else:
                    v = ~v
                    if parent[v] != -1:
                        low[parent[v]] = min(low[parent[v]], low[v])
                    if low[v] == order[v]:
                        while True:
                            w = S.pop()
                            order[w] = n
                            gp[w] = gp_num
                            if w==v: break
                        gp_num += 1


    scc = [[] for _ in range(gp_num)]
    for i in range(n):
        gp[i] = gp_num-gp[i]-1
        scc[gp[i]].append(i)
    
    return scc, gp, gp_num

n = int(input())
g = [[] for _ in range(n)]
diff = [0]*n
for i in range(n):
    l,s = map(int,input().split())
    g[s-1].append(i)
    diff[i] = l

scc,gp,m = SCC_Tarjan(g)
indegree = [0]*m
for v in range(n):
    for c in g[v]:
        if gp[v] != gp[c]:
            indegree[gp[c]] = 1

ans = sum(diff)
for i in range(m):
    if indegree[i] == 0:
        ans += min(diff[k] for k in scc[i])
print(ans/2)