Submission #73611878

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Source Code Expand

#include <bits/stdc++.h>
#define _ ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
typedef long long ll;
using namespace std;
#define int ll

int solve() {
	int n, m, res = 0; cin >> n >> m;

	set<array<int, 2>> S;
	for (int i = 0, a, b; i < m; i++) {
		cin >> a >> b;
		res += S.count({b, a});
		S.insert({a, b});
	}
	cout << res << endl;

	return(0);
}

signed main()
{
    _;

	int t = 1; //cin >> t;
	while (t--) {
		solve();
	}
    
    return(0);
}

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