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RCC318B.cpp
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RCC318B.cpp
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/*
* J1K7_7
*
* You can use my contents on a Creative Commons - Attribution 4.0 International - CC BY 4.0 License. XD
* - JASKAMAL KAINTH
*/
#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <cstring>
#include <cassert>
#include <list>
#include <map>
#include <unordered_map>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <utility>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <limits>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<long long> vll;
#define left(x) (x << 1)
#define right(x) (x << 1) + 1
#define mid(l, r) ((l + r) >> 1)
#define mp make_pair
#define pb push_back
#define all(a) a.begin(),a.end()
#define debug(x) {cerr <<#x<<" = " <<x<<"\n"; }
#define debug2(x, y) {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<"\n";}
#define debug3(x, y, z) {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<", "<<#z<<" = "<<z<<"\n";}
#define debug4(x, y, z, w) {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<", "<<#z<<" = "<<z<<", "<<#w << " = " <<w <<"\n";}
#define ss second
#define ff first
#define m0(x) memset(x,0,sizeof(x))
const int mod=1e9+7;
template<class T> inline T gcd(T a,T b){ll t;while(b){a=a%b;t=a;a=b;b=t;}return a;}
template<class T> inline T lcm(T a,T b){return a/gcd(a,b)*b;}
template<typename T, typename S> T expo(T b, S e, const T &m){if(e <= 1)return e == 0?1: b;\
return (e&1) == 0?expo((b*b)%m, e>>1, m): (b*expo((b*b)%m, e>>1, m))%m;}
template<typename T> T modinv(T a) { return expo(a, mod-2, mod); }
inline int nextint(){ int x; scanf("%d",&x); return x; }
inline ll nextll(){ ll x; scanf("%lld",&x); return x; }
const ll mx_ll = numeric_limits<ll> :: max();
const int mx_int = numeric_limits<int> :: max();
const long double PI = (long double)(3.1415926535897932384626433832795);
const int maxn = 4e3+6;
int adj[maxn][maxn];
vector<int> G[maxn];
vector<pii> edge;
int main()
{
ios_base::sync_with_stdio(false); cin.tie(0);
int n , m; cin >> n >> m;
while(m--)
{
int u , v; cin >> u >> v;
G[u].pb(v);
G[v].pb(u);
edge.pb({u,v});
adj[u][v] = 1;
adj[v][u] = 1;
}
int fans = mx_int;
for(auto &e : edge)
{
int u = e.ff;
int v = e.ss;
int recog = G[u].size()-1 + G[v].size()-1;
int tans;
for(int i = 1; i <= n; i++)
{
if(adj[i][u] && adj[i][v])
{
tans = recog + G[i].size()-2;
tans -= 2;
fans = min(fans,tans);
}
}
}
if(fans == mx_int)
cout << "-1\n";
else
cout << fans << "\n";
return 0;
}