import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.NoSuchElementException;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {
		long t = System.currentTimeMillis();
		new Main().run();
		System.err.println(System.currentTimeMillis() - t);
	}

	class DJSet{
		int n;
		int[] upper;
		
		public DJSet(int n) {
			this.n=n;
			upper=new int[n];
			Arrays.fill(upper, -1);
		}
		
		int root(int x) {
			return upper[x]<0?x:(upper[x]=root(upper[x]));
		}
		
		boolean equiv(int x,int y) {
			return root(x)==root(y);
		}
		
		void setUnion(int x,int y) {
			x=root(x);y=root(y);
			if(x==y)return;
			if(upper[x]<upper[y]) {
				x^=y;y^=x;x^=y;
			}
			upper[y]+=upper[x];
			upper[x]=y;
		}
		
		int sz(int x) {
			return -upper[root(x)];
		}
	}
	
	void run() {
		FastScanner sc = new FastScanner();
		int N=sc.nextInt();
		int M=sc.nextInt();
		int[] deg=new int[N];
		DJSet ds=new DJSet(N);
		for(int i=0;i<M;++i) {
			int a=sc.nextInt();
			int b=sc.nextInt();
			deg[a]++;
			deg[b]++;
			ds.setUnion(a, b);
		}
		boolean ans=true;
		int odd=0;
		for(int i=0;i<deg.length;++i)if(deg[i]%2==1)++odd;
		ans&=odd==0||odd==2;
		int sz=0;
		for(int i=0;i<N;++i)if(deg[i]>0)++sz;
		for(int i=0;i<N;++i) {
			if(deg[i]>0)ans&=ds.sz(i)==sz;
		}
		System.out.println(ans?"YES":"NO");
	}

	
	
	static void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}
	
	
class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    
    public int nextInt() {
    	return (int)nextLong();
    }
}