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@@ -0,0 +1,45 @@
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+#include <bits/stdc++.h>
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+using namespace std;
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+int main(){
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+ int n, m;
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+ cin >> n >> m;
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+ int degree[n+1] = {0};
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+ int s, e;
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+ cin >> s >> e;
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+ for(int i = 1; i <= m; i++){
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+ int x, y;
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+ cin >> x >> y;
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+ degree[x]++;
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+ degree[y]++;
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+ }
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+ int a = 0, b = 0;
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+ int flag = 1;
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+ if(s == e){
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+ for(int i= 1; i <= n; i++){
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+ if(degree[i]%2==1){
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+ flag = 0;
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+ break;
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+ }
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+ }
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+ }else{
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+ for(int i = 1; i <= n; i++){
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+ if(i == s || i == e){
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+ if(degree[i] % 2 == 0){
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+ flag = 0;
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+ break;
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+ }
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+ }else{
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+ if(degree[i] % 2 == 1){
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+ flag = 0;
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+ break;
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+ }
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+ }
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+ }
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+ }
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+ if(flag){
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+ cout << "YES" << endl;
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+ }else{
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+ cout << "NO" << endl;
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+ }
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+
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+}
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