import sys
input = sys.stdin.readline
n, m = [int(i) for i in input().split()]
p = []
l = []
ans = 'YES'
for i in range(m):
a, b =[ int(i) for i in input().split()]
if i==0 : l.append(a); l.append(b)
if a not in l and b not in l :
if len(l) == 4 : ans = "NO"
else : l.append(a); l.append(b)
p.append((a, b))
if ans == "NO" : print(ans)
else :
res = "NO"
if len(l) == 2 : print("YES")
else :
for i in range(4):
for j in range(i+1, 4):
x, y = l[i], l[j]
c = "YES"
for k in range(m):
if p[k][0] not in (x, y) and p[k][1] not in (x, y) :
c = "NO"
break
if c=="YES" : res = "YES"; break
if res == "YES": break
print(res)#include <iostream>
#include <algorithm>
#include <utility>
#include <cmath>
#include <stack>
#include <cstdlib>
#include <vector>
#include <queue>
#include <set>
#include <map>
using namespace std;
#define ll long long
#define endl "\n"
#define pb(x) push_back(x)
#define all(v) (v).begin(), (v).end()
#define MAX INT64_MAX
//============================================================================================================//
//-----------------------------------directions array---------------------------------------------------------//
int di[] = {1, -1, 0, 0, 1, -1, 1, -1};
int dj[] = {0, 0, 1, -1, 1, -1, -1, 1};
int dx[] = {-1, 1, 0, 0};
int dy[] = {0, 0, -1, 1};
//============================================================================================================//
//-----------------------------------some constant--------------------------------------------------------------
const int SZ = 2 * (1e5 + 9);
const ll CON = (1e18);
const ll inf = (1 << 30);
const int MOD = (1e9 + 7);
const int M = (3005);
//============================================================================================================//
//-----------------------------------some functions--------------------------------------------------------------
void FAST() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); }
void Mostafa()
{
#ifndef ONLINE_JUDGE
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
freopen("errors.txt","w",stderr);
#endif
}
ll gcd(ll a, ll b)
{ return b == 0 ? a : gcd(b, a % b); }
ll lcm(ll a, ll b)
{ return a / gcd(a, b) * b; }
//============================================================================================================//
//---------------------------------------------------------------------------------------------------------------
bool so(int x,int n, vector<pair<int ,int>>v1,int v)
{
int arr[v+10]{0};
int bad =0,ma=0;
for (int i = 0; i < n; ++i) {
if (x != v1[i].first && x != v1[i].second)
{
bad++;
if (v1[i].first != v1[i].second)
{
arr[v1[i].first]++;
arr[v1[i].second]++;
}
else arr[v1[i].first]++;
ma = max ({arr[v1[i].first],ma,arr[v1[i].second]});
}
}
// cout <<bad <<" "<<ma<<endl;
return (bad==ma);
}
void solve() {
int n,v;
cin >>v>>n;
vector<pair<int ,int>>v1(n);
for (int i = 0; i < n; ++i) {
cin >> v1[i].first>>v1[i].second;
}
if (so(v1[0].first,n,v1,v) ||so(v1[0].second,n,v1,v) )
cout <<"YES";
else cout <<"NO";
}
int main ()
{
FAST();
Mostafa();
int q = 1;
// cin >>q;
while(q--)
{
solve();
}
}
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1728C - Digital Logarithm | 1728D - Letter Picking |
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5D - Follow Traffic Rules | 1272A - Three Friends |
1632D - New Year Concert | 1400D - Zigzags |
716C - Plus and Square Root | 412A - Poster |
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1398C - Good Subarrays | 629A - Far Relative’s Birthday Cake |
1166A - Silent Classroom | 1000B - Light It Up |
218B - Airport | 1463B - Find The Array |