from sys import stdin
n, *indata = map(int, stdin.read().split())
offset = 0

gnum = [0 for i in range((10**5)*2+1)]
ginv = [0 for i in range((10**5)*2+1)]
g = [[] for i in range((10**5)*2+1)]
appeared = set()
for i in range(n):
    s, t = indata[offset + 2*i],indata[offset + 2*i+1]
    g[s].append(t)
    g[t].append(s)
    gnum[s] += 1
    ginv[t] += 1
    appeared.add(s)
    appeared.add(t)

check = [False for i in range((10**5)*2+1)]
kari = appeared.pop()
que = [kari]
check[kari] = True
while que:
    now = que.pop()
    for i in g[now]:
        if not check[i]:
            que.append(i)
            check[i] = True

for i in appeared:
    if not check[i]:
        print("{}".format(0))
        exit()

plusused = False
minusused = False
for i in range(1,(10**5)*2+1):
    if abs(gnum[i] - ginv[i]) >= 2:
        print("{}".format(0))
        exit()
    elif gnum[i] - ginv[i] == 1:
        if plusused:
            print("{}".format(0))
            exit()
        else:
            plusused = True
    elif gnum[i] - ginv[i] == 1:
        if minusused:
            print("{}".format(0))
            exit()
        else:
            minusused = True

if plusused:
    print("{}".format(1))
    exit()

ans = 0
for i in range(1,(10**5)*2+1):
    if gnum[i]:
        ans += 1
print("{}".format(ans))