#include <bits/stdc++.h>
using ll = long long;
#define FOR(i, a, b) for (int i = (a); i < int(b); ++i)
#define RFOR(i, a, b) for (int i = (b) - 1; i >= int(a); --i)
#define rep(i, n) FOR(i, 0, n)
#define rep1(i, n) FOR(i, 1, int(n) + 1)
#define rrep(i, n) RFOR(i, 0, n)
#define rrep1(i, n) RFOR(i, 1, int(n) + 1)
#define all(c) begin(c), end(c)

std::string highlight(std::string s) {
#ifdef _MSC_VER
    return s;
#else
    return "\033[33m" + s + "\033[0m";
#endif
}

#ifdef LOCAL
#define dump(...)                                         \
    do {                                                  \
        std::ostringstream os;                            \
        os << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; \
        print_to(os, ", ", "\n", __VA_ARGS__);            \
        std::cerr << highlight(os.str());                 \
    } while (0)
#define dump_(a)                                          \
    do {                                                  \
        std::ostringstream os;                            \
        os << __LINE__ << ":\t" << #a << " = [";          \
        print_to_(os, ", ", "]\n", all(a));               \
        std::cerr << highlight(os.str());                 \
    } while (0)
#else
#define dump(...)
#define dump_(...)
#endif

template <typename T>
void print_to(std::ostream &os, const char *, const char *tail, const T &fst) {
    os << fst << tail;
}
template <typename Fst, typename... Rst>
void print_to(std::ostream &os, const char *del, const char *tail, const Fst &fst, const Rst &... rst) {
    os << fst << del;
    print_to(os, del, tail, rst...);
}
template <typename Iter>
void print_to_(std::ostream &os, const char *del, const char *tail, Iter bgn, Iter end) {
    for (Iter it = bgn; it != end;) {
        os << *it;
        if (++it != end) {
            os << del;
        } else {
            os << tail;
        }
    }
}
template <typename Fst, typename... Rst>
void println(const Fst &fst, const Rst &... rst) {
    print_to(std::cout, "\n", "\n", fst, rst...);
}
template <typename Fst, typename... Rst>
void print(const Fst &fst, const Rst &... rst) {
    print_to(std::cout, " ", "\n", fst, rst...);
}
template <typename Iter>
void println_(Iter bgn, Iter end) {
    print_to_(std::cout, "\n", "\n", bgn, end);
}
template <typename Iter>
void print_(Iter bgn, Iter end) {
    print_to_(std::cout, " ", "\n", bgn, end);
}

// const int MOD = 1000000007;
namespace trush {
    int _ = (std::cout.precision(10), std::cout.setf(std::ios::fixed), std::cin.tie(0),
             std::ios::sync_with_stdio(0), 0);
}

using namespace std;

struct uf_tree {
    std::vector<int> parent;
    int __size;
    uf_tree(int size_) : parent(size_, -1), __size(size_) {}
    void unite(int x, int y) {
        if ((x = find(x)) != (y = find(y))) {
            if (parent[y] < parent[x]) std::swap(x, y);
            parent[x] += parent[y];
            parent[y] = x;
            __size--;
        }
    }
    bool is_same(int x, int y) { return find(x) == find(y); }
    int find(int x) { return parent[x] < 0 ? x : parent[x] = find(parent[x]); }
    int size(int x) { return -parent[find(x)]; }
    int size() { return __size; }
};

int main() {
    int n, m;
    while (cin >> n >> m) {
        vector<int> deg(n);
        uf_tree ut(n);
        set<int> s;
        rep(i, m) {
            int a, b;
            cin >> a >> b;
            ++deg[a];
            ++deg[b];
            ut.unite(a, b);
            s.insert(a);
            s.insert(b);
        }
        dump_(deg);
        int odd = 0;
        bool yes = odd <= 2 && ut.size() == (int)s.size();
        print(yes ? "YES" : "NO");
    }
}