#include class DisjointSets { public: DisjointSets(const std::size_t v) : parent(v), rank(v, 0), size(v, 1) { std::iota(parent.begin(), parent.end(), 0); } bool same(const std::size_t a, const std::size_t b) { return find(a) == find(b); } void unite(std::size_t a, std::size_t b) { a = find(a), b = find(b); if (a == b) { return; } if (rank[a] < rank[b]) { std::swap(a, b); } if (rank[a] == rank[b]) { rank[a]++; } size[a] += size[b], parent[b] = a; } std::size_t getSize(const std::size_t a) { return size[find(a)]; } std::size_t find(const std::size_t a) { return parent[a] == a ? a : parent[a] = find(parent[a]); } private: std::vector parent, rank, size; }; int main() { int N; std::cin >> N; DisjointSets uf(N); std::vector a(N); for (int i = 0; i < N; i++) { std::cin >> a[i], uf.unite(i, a[i] - 1); } std::vector used(N, false); int even = 0; for (int i = 0; i < N; i++) { if (not used[uf.find(i)]) { used[uf.find(i)] = true, even += (uf.getSize(i) % 2 == 0 ? 1 : 0); } } std::cout << (even % 2 == 0 ? "Yes" : "No") << std::endl; return 0; }