#include <stdio.h>
#include <vector>


inline int min(int a, int b) {
	return a < b ? a : b;
}


struct SCC {
	
	int N;
	std::vector<std::vector<int>> edge;
	std::vector<int> scc, visit, low, in_stack, stack;
	int scc_no, t, top;
	
	void init(int _N) {
		N = _N;
		edge.clear(), edge.resize(N);
		scc.clear(), visit.clear(), low.clear(), in_stack.clear(), stack.clear();
		scc_no = t = top = 0;
	}
	
	void add_edge(int a, int b) {
		edge[a].push_back(b);
	}
	
	const std::vector<int>& slove() {
		scc.clear(), scc.resize(N);
		visit.clear(), visit.resize(N);
		low.clear(), low.resize(N);
		in_stack.clear(), in_stack.resize(N);
		stack.clear(), stack.resize(N);
		scc_no = t = top = 0;
		for (int i = 0; i < N; ++i) {
			if (!visit[i]) {
				_scc_dfs(i);
			}
		}
		return scc;
	}
	
	void _scc_dfs(int i) {
		visit[i] = low[i] = ++t;
		stack[top++] = i, ++in_stack[i];
		for (int j : edge[i]) {
			if (!visit[j]) {
				_scc_dfs(j);
			}
			if (in_stack[j]) {
				low[i] = min(low[i], low[j]);
			}
		}
		if (visit[i] == low[i]) {
			int j;
			do {
				j = stack[--top];
				in_stack[j] = 0;
				scc[j] = scc_no;
			} while(j != i);
			++scc_no;
		}
	}
	
};


struct Chain {
	
	int N;
	std::vector<std::vector<int>> edge;
	std::vector<int> visit, count;
	
	void init(int _N) {
		N = _N;
		edge.clear(), edge.resize(N);
		visit.clear(), count.clear();
	}
	
	void add_edge(int a, int b) {
		edge[a].push_back(b);
	}
	
	bool check(int start_from) {
		visit.clear(), visit.resize(N);
		count.clear(), count.resize(N);
		return _check_dfs(start_from) == N;
	}
	
	int _check_dfs(int i) {
		++visit[i];
		int m = 0;
		for (int j : edge[i]) {
			if (!visit[j]) {
				_check_dfs(j);
			}
			if (m < count[j]) {
				m = count[j];
			}
		}
		count[i] = m+1;
		return count[i];
	}
	
};


int main() {
	
	SCC scc;
	int N, M;
	
	scanf("%d%d", &N, &M);
	
	scc.init(N);
	while (M--) {
		int a, b;
		scanf("%d%d", &a, &b);
		scc.add_edge(a-1, b-1);
	}
	
	const std::vector<int> &scc_group = scc.slove();
	
	Chain chain;
	chain.init(scc.scc_no);
	for (int i = 0; i < N; ++i) {
		for (int j : scc.edge[i]) {
			chain.add_edge(scc_group[i], scc_group[j]);
		}
	}
	
	if (chain.check(scc_group[0])) {
		puts("Yes");
	}
	else {
		puts("No");
	}
	
}