#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int a[1005][1005];
int vis[1005];
int qu[100005], front, tail;
void init()
{
    memset(a, 0, sizeof(a));
    memset(vis, 0, sizeof(vis));
    front = tail = 0;
}
int main()
{
    int t, n, m, i, j;
    while(scanf("%d %d", &n, &m) != EOF)
    {
        init();
        for(i = 1; i <= m; i++)
        {
            int u, v;
            scanf("%d %d", &u, &v);
            a[u][v] = 1;
        }
        qu[tail++] = n;
        int flag = 0;
        while(front < tail)
        {
            int w = qu[front++];
            vis[w] = 1;
            if(w == 1){flag = 1;break;}
            for(i = 1; i <= n; i++)
            {
                if(a[w][i] == 1 && vis[i] == 0){qu[tail++] = i; vis[i] = 1;}
            }
        }
        if(flag == 1)printf("YES\n");
        else printf("NO\n");
    }
    return 0;
}