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| #include <bits/stdc++.h>
#pragma optimization_level 3
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")
using namespace std;
struct PairHash {inline std::size_t operator()(const std::pair<int, int> &v) const { return v.first * 31 + v.second; }};
#define Code ios_base::sync_with_stdio(false);
#define By ios::sync_with_stdio(0);
#define Sumfi cout.tie(NULL);
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const ld PI = 3.14159265358979323846;
const ll INF = 1e18;
const ld EPS = 1e-9;
const ll MAX_N = 40404;
const ll mod = 1e9 + 7;
typedef pair<ll, ll> pll;
typedef vector<pll> vpll;
typedef array<ll,3> all3;
typedef array<ll,5> all5;
typedef vector<all3> vall3;
typedef vector<all5> vall5;
typedef vector<ld> vld;
typedef vector<ll> vll;
typedef vector<vll> vvll;
typedef vector<int> vi;
typedef pair<string, string> pss;
typedef vector<pss> vpss;
typedef vector<string> vs;
typedef vector<vs> vvs;
typedef unordered_set<ll> usll;
typedef unordered_set<pll, PairHash> uspll;
typedef unordered_map<ll, ll> umll;
typedef unordered_map<pll, ll, PairHash> umpll;
#define rep(i,m,n) for(ll i=m;i<n;i++)
#define rrep(i,m,n) for(ll i=n;i>=m;i--)
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define ASCEND(a) iota(all(a),0)
#define sz(x) ll((x).size())
#define pyes cout<<"YES\n";
#define pno cout<<"NO\n";
#define pneg1 cout<<"-1\n";
#define CASE(x) cout<<"Case #"<<x<<": ";
template <typename T>
void print(T &&t) { cout << t << "\n"; }
template<typename T>
void printv(vector<T>v){ll n=v.size();rep(i,0,n)cout<<v[i]<<" ";cout<<"\n";}
void fileIO() {freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);}
ll __gcd(ll x, ll y) { return !y ? x : __gcd(y, x % y); }
ll __lcm(ll x, ll y) { return x * y / __gcd(x,y); }
ll modpow(ll n, ll x, ll MOD = mod) { if(!x) return 1; ll res = modpow(n,x>>1,MOD); res = (res * res) % MOD; if(x&1) res = (res * n) % MOD; return res; }
vll adj[55];
ll id = 1;
ll mi[55], vis[55];
vvll st;
vector<vvll> bcc;
void dfs(ll u, ll par) {
mi[u] = vis[u] = id++;
for(auto& v : adj[u]) {
if(v == par) continue;
if(vis[u] > vis[v]) st.push_back({u,v});
if(vis[v]) mi[u] = min(mi[u], vis[v]);
else {
dfs(v,u);
mi[u] = min(mi[u], mi[v]);
if(mi[v] >= vis[u]) {
bcc.emplace_back();
while(!st.empty()) {
auto e = st.back(); st.pop_back();
bcc.back().push_back(e);
if(e[0] == u and e[1] == v) break;
}
}
}
}
}
ll solve(vpll& E, ll n) {
rep(i,0,sz(E)) {
auto [u,v] = E[i];
adj[u].push_back(v);
adj[v].push_back(u);
}
rep(i,1,n+1) {
if(!vis[i])
dfs(i,-1);
}
ll res = 0;
rep(i,0,sz(bcc)) {
res += sz(bcc[i]) == 1;
}
return res;
}
int main() {
Code By Sumfi
cout.precision(12);
ll tc = 1;
rep(i,1,tc+1) {
ll n,m;
cin>>n>>m;
vpll A(m);
rep(i,0,m) cin>>A[i].first>>A[i].second;
print(solve(A,n));
}
return 0;
}
|
