mod = 998244353


def main():
    import sys
    from collections import deque
    input = sys.stdin.readline

    N = int(input())
    adj = [[] for _ in range(N + 1)]
    for _ in range(N - 1):
        a, b = map(int, input().split())
        adj[a].append(b)
        adj[b].append(a)

    que = deque()
    que.append(1)
    seen = [-1] * (N+1)
    seen[1] = 0
    par = [0] * (N+1)
    child = [[] for _ in range(N+1)]
    seq = []
    while que:
        v = que.popleft()
        seq.append(v)
        for u in adj[v]:
            if seen[u] == -1:
                seen[u] = seen[v] + 1
                par[u] = v
                child[v].append(u)
                que.append(u)
    seq.reverse()

    v0 = seq[0]
    que = deque()
    que.append(v0)
    seen = [-1] * (N+1)
    seen[v0] = 0
    par = [0] * (N+1)
    child = [[] for _ in range(N+1)]
    seq = []
    while que:
        v = que.popleft()
        seq.append(v)
        for u in adj[v]:
            if seen[u] == -1:
                seen[u] = seen[v] + 1
                par[u] = v
                child[v].append(u)
                que.append(u)
    seq.reverse()

    v1 = seq[0]
    D = seen[v1]
    if D & 1:
        v = v1
        for _ in range(D // 2):
            v = par[v]
        vl = v
        vr = par[v]
        vl_ori = vl
        vr_ori = vr

        que = deque()
        que.append(vl)
        seen = [-1] * (N+1)
        seen[vl] = 0
        par = [0] * (N+1)
        child = [[] for _ in range(N+1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if u == vr_ori:
                    continue
                if seen[u] == -1:
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()
        vl = seq[0]
        que = deque()
        que.append(vl)
        seen = [-1] * (N + 1)
        seen[vl] = 0
        par = [0] * (N + 1)
        child = [[] for _ in range(N + 1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if seen[u] == -1:
                    if u == vr_ori:
                        continue
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()
        dl = seen[seq[0]]

        que = deque()
        que.append(vr)
        seen = [-1] * (N + 1)
        seen[vr] = 0
        par = [0] * (N + 1)
        child = [[] for _ in range(N + 1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if seen[u] == -1:
                    if u == vl_ori:
                        continue
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()
        vr = seq[0]
        que = deque()
        que.append(vr)
        seen = [-1] * (N + 1)
        seen[vr] = 0
        par = [0] * (N + 1)
        child = [[] for _ in range(N + 1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if seen[u] == -1:
                    if u == vl_ori:
                        continue
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()
        dr = seen[seq[0]]

        print((dl + 1) // 2 + (dr + 1) // 2 + 1)
    else:
        ans = N * 2
        v = v1
        for _ in range(D // 2):
            v = par[v]
        v0 = v
        que = deque()
        que.append(v0)
        seen = [-1] * (N+1)
        seen[v0] = 0
        par = [0] * (N+1)
        child = [[] for _ in range(N+1)]
        seq = []
        while que:
            v = que.popleft()
            seq.append(v)
            for u in adj[v]:
                if seen[u] == -1:
                    seen[u] = seen[v] + 1
                    par[u] = v
                    child[v].append(u)
                    que.append(u)
        seq.reverse()

        subtree_len = [(0, 0)]
        for c in child[v0]:
            que = deque()
            seq = []
            que.append(c)
            while que:
                v = que.popleft()
                for vv in child[v]:
                    que.append(vv)
                seq.append(v)
            subtree_len.append((seen[seq[-1]], c))
        subtree_len.sort(key=lambda x: x[0], reverse=True)

        for c in child[v0]:
            cc = c
            que = deque()
            que.append(cc)
            seen = {}
            seen[cc] = 0
            seq = []
            while que:
                v = que.popleft()
                seq.append(v)
                for u in adj[v]:
                    if u == v0:
                        continue
                    if u not in seen:
                        seen[u] = seen[v] + 1
                        que.append(u)
            seq.reverse()
            cc = seq[0]
            que = deque()
            que.append(cc)
            seen = {}
            seen[cc] = 0
            seq = []
            while que:
                v = que.popleft()
                seq.append(v)
                for u in adj[v]:
                    if u == v0:
                        continue
                    if u not in seen:
                        seen[u] = seen[v] + 1
                        que.append(u)
            seq.reverse()
            dc = seen[seq[0]]

            if c == subtree_len[0][1]:
                dc2 = subtree_len[1][1] + subtree_len[2][1]

            elif c == subtree_len[1][1]:
                dc2 = subtree_len[0][1] + subtree_len[2][1]
            else:
                dc2 = subtree_len[0][1] + subtree_len[1][1]
            ans = min(ans, (dc + 1) // 2 + (dc2 + 1) // 2 + 1)
        print(ans)


if __name__ == '__main__':
    main()