10
4 2
7 4
2 6
2 5
4 8
10 3
2 9
9 1
5 10
 10
5 10
7 8
8 3
2 6
3 2
9 7
4 5
10 1
6 4
 4
4 1
4 3
4 2
 3
3 1
1 2
 9
1 2
1 3
1 4
1 5
1 6
6 7
6 8
8 9
 5
1 5
2 3
2 4
1 2
 8
6 1
4 7
4 8
8 5
7 6
4 3
4 2
 7
5 6
5 7
5 1
7 4
6 3
3 2
 3
1 3
3 2
 2
1 2
 5
5 4
4 3
3 1
5 2
 6
1 6
3 1
6 4
5 3
2 5
 11
8 9
2 7
1 11
3 2
9 1
8 5
8 6
5 4
4 10
8 3
 11
11 9
6 7
7 1
8 11
5 6
3 5
9 3
10 8
2 4
4 10
 12
12 6
6 7
8 11
4 8
10 4
12 3
2 10
6 2
12 9
4 1
9 5

-1
 9
 1
 1
 3
 3
 -1
 -1
 1
 1
 1
 5
 1
 5
 -1

import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

def LI(): return list(map(int, input().split()))
def II(): return int(input())
def LS(): return input().split()
def S(): return input()


def main():
    n = II()
    d = collections.defaultdict(set)
    for _ in range(n-1):
        a,b = LI()
        d[a].add(b)
        d[b].add(a)

    def path(t,s):
        ps = set()
        dt = list(d[t])
        for k in dt:
            if k == s:
                continue
            f,pt = path(k,t)
            if f == False:
                return (False, pt)
            if pt in ps:
                d[k] -= set([t])
                d[t] -= set([k])
            ps.add(pt)
        if s == -1 and len(ps) == 2:
            return (True, sum(ps))
        if len(ps) > 1:
            return (False, t)
        if len(ps) == 0:
            return (True, 1)
        return (True,list(ps)[0] + 1)

    f,t = path(1,-1)
    if f:
        while t%2 == 0:
            t//=2
        return t

    f,t = path(t,-1)
    if f:
        while t%2 == 0:
            t//=2
        return t

    return -1

print(main())
