#include <iostream>
#include <vector>

using namespace std;

class BipartiteUnionFind
{
protected:
    vector<size_t> root_of, size_of, unconnectables_of;
    vector<bool> color_of;
    size_t group;
    virtual size_t retrieve_true_root_of(const size_t index) { return root_of[index] == index ? index : retrieve_true_root_of(root_of[index]), color_of[index] = color_of[index] ^ color_of[root_of[index]], root_of[index] = root_of[root_of[index]]; }

public:
    BipartiteUnionFind(const size_t N) : root_of(N), size_of(N, 1), unconnectables_of(N, 1), color_of(N, false), group(N) { for (size_t i = 0; i != N; ++i) root_of[i] = i; }
    virtual bool is_connected(const size_t a, const size_t b) { return retrieve_true_root_of(a) == retrieve_true_root_of(b); }
    virtual bool is_connectable(const size_t a, const size_t b) { return color_of[a] != color_of[b]; }
    virtual bool merge(const size_t a, const size_t b)
    {
        if (retrieve_true_root_of(a) != retrieve_true_root_of(b))
        {
            unconnectables_of[root_of[a]] += color_of[a] ? count_unconnectables_of(b) : size_of[root_of[b]] - count_unconnectables_of(b);
            color_of[root_of[b]] = !(color_of[a] ^ color_of[b]), color_of[b] = !color_of[a];
            size_of[root_of[a]] += size_of[root_of[b]];
            root_of[b] = root_of[root_of[b]] = root_of[a];
            --group;
            return true;
        }
        else
            return false;
    }
    size_t size_of_group_of(const size_t index) { return size_of[retrieve_true_root_of(index)]; }
    size_t groups() { return group; }
    size_t count_unconnectables_of(const size_t index) { return retrieve_true_root_of(index), color_of[index] ? size_of[root_of[index]] - unconnectables_of[root_of[index]] : unconnectables_of[root_of[index]]; }
};

int main()
{
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n, m, a, b, i;
    cin >> n >> m;
    BipartiteUnionFind buf(n);
    for (i = 0; i != m; ++i)
    {
        cin >> a >> b, --a, --b;
        if (buf.is_connected(a, b))
        {
            if (!buf.is_connectable(a, b))
            {
                for (++i; i != m; ++i) cin >> a >> b;
                cout << "No\n";
                return 0;
            }
        }
        else buf.merge(a, b);
    }

    cout << "Yes\n";
    return 0;
}