from sys import stdin

def main():
    input = stdin.read().split()
    idx = 0
    n = int(input[idx])
    idx += 1
    m = int(input[idx])
    idx += 1
    adj = [[] for _ in range(n + 1)]
    for _ in range(m):
        u = int(input[idx])
        idx += 1
        v = int(input[idx])
        idx += 1
        adj[u].append(v)
        adj[v].append(u)
    # Collect neighbors of vertex 1
    s = set()
    for neighbor in adj[1]:
        s.add(neighbor)
    if not s:
        print("NO")
        return
    found = False
    # Check each neighbor of 1
    for a in s:
        # DFS stack: (current node, depth, visited set)
        stack = [(a, 0, {1, a})]
        while stack:
            node, depth, visited = stack.pop()
            if depth == 3:
                if node in s and node != a:
                    found = True
                    break
                continue
            # Explore neighbors in reverse order to process smaller indices first (stack order)
            for neighbor in reversed(adj[node]):
                if neighbor == 1:
                    continue
                if neighbor not in visited:
                    new_visited = visited.copy()
                    new_visited.add(neighbor)
                    stack.append((neighbor, depth + 1, new_visited))
        if found:
            break
    print("YES" if found else "NO")

if __name__ == "__main__":
    main()