#include /* strict input checker */ template Integer read_int() { static_assert(std::numeric_limits::is_specialized); int c = getchar(), sign = 0; Integer res = 0; if (c == '-') sign = 1, c = getchar(); assert('0' <= c && c <= '9'); if (sign) assert(c != '0'); res = c - '0'; while (1) { c = getchar(); if (c < '0' || c > '9') break; assert(res < std::numeric_limits::max() / 10); // avoid overflow assert(res); // no leading-zero res = res * 10 + (c - '0'); } ungetc(c, stdin); return sign ? -res : res; } void read_linebreak() { int c = getchar(); if (c == '\r') c = getchar(); assert(c == '\n'); } struct UnionFind { std::vector data; UnionFind (int size) : data(size, -1) {} bool unite(int x, int y) { x = root(x); y = root(y); if (x != y) { if (data[y] < data[x]) std::swap(x, y); data[x] += data[y]; data[y] = x; } return x != y; } bool same(int x, int y) { return root(x) == root(y); } int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); } int size(int x) { return -data[root(x)]; } bool connected() { return size(0) == (int) data.size(); } }; int main() { int n = read_int(); read_linebreak(); assert(1 <= n && n <= 300000); UnionFind uni(n); for (int i = 1; i < n; i++) { int a = read_int(); assert(getchar() == ' '); int b = read_int(); read_linebreak(); assert(1 <= a && a < b && b <= n); assert(uni.unite(a - 1, b - 1)); } assert(getchar() == EOF); return 0; }