1 #include <iostream>
2 #include <queue>
3 #include <stack>
4 #include <cstdio>
5 #include <vector>
6 #include <map>
7 #include <set>
8 #include <bitset>
9 #include <algorithm>
10 #include <cmath>
11 #include <cstring>
12 #include <cstdlib>
13 #include <string>
14 #include <sstream>
15 #include <time.h>
16 #define x first
17 #define y second
18 #define pb push_back
19 #define mp make_pair
20 #define lson l,m,rt*2
21 #define rson m+1,r,rt*2+1
22 #define mt(A,B) memset(A,B,sizeof(A))
23 #define lowbit(x) (x&(-x))
24 using namespace std;
25 typedef long long LL;
26 //const double PI = acos(-1);
27 const int N=2e5+10;
28 //const int M=1e6+10;
29 const LL mod=1e9+9;
30 const int inf = 0x3f3f3f3f;
31 const LL INF=0x3f3f3f3f3f3f3f3fLL;
32 const double esp=1e-10;
33 const int MAXN=500010;
34 int vis[N],top=0,head[N],ans[N],pre[N],vik[2*N],cnt=0;
35 struct node
36 {
37 int u,v,next;
38 }E[N*2];
39 void add(int u,int v)
40 {
41 E[top].u=u;
42 E[top].v=v;
43 E[top].next=head[u];
44 head[u]=top++;
45 }
46 int found(int x)
47 {
48 if(x==pre[x])return x;
49 else return pre[x]=found(pre[x]);
50 }
51 void unite(int x,int y)
52 {
53 int fx=found(x);
54 int fy=found(y);
55 if(fx!=fy)pre[fx]=fy;
56 }
57 void dfs(int u)
58 {
59 while(head[u]!=-1)
60 {
61 if(!vik[head[u]])
62 {
63 vik[head[u]]=1;
64 vik[head[u]^1]=1;
65 int i=head[u];
66 dfs(E[i].v);
67 ans[cnt++]=i;
68 }
69 else head[u]=E[head[u]].next;
70 }
71 }
72 int main()
73 {
74 #ifdef Local
75 freopen("data.txt","r",stdin);
76 #endif
77 //ios::sync_with_stdio(false);
78 //cin.tie(0);
79 int n,m,u,v,flag=0,num=0;
80 scanf("%d%d",&n,&m);
81 mt(vis,0);
82 mt(vik,0);
83 mt(head,-1);
84 for(int i=1;i<=n;i++)pre[i]=i;
85 for(int i=1;i<=m;i++)
86 {
87 scanf("%d%d",&u,&v);
88 add(u,v);
89 add(v,u);
90 unite(u,v);
91 vis[u]++;vis[v]++;
92 }
93 for(int i=1;i<=n;i++)
94 {
95 if(vis[i]%2)flag=1;
96 }
97 for(int i=1;i<=n;i++)
98 {
99 if(pre[i]==i)num++;
100 }
101 if(num>1)flag=1;
102 if(flag)
103 {
104 puts("NO");return 0;
105 }
106 else
107 {
108 dfs(1);
109 puts("YES");
110 sort(ans,ans+m);
111 for(int i=0;i<m;i++)
112 {
113 printf("%d %d\n",E[ans[i]].u,E[ans[i]].v);
114 }
115 }
116 return 0;
117 #ifdef Local
118 cerr << "time: " << (LL) clock() * 1000 / CLOCKS_PER_SEC << " ms" << endl;
119 #endif
120 }
