a.cpp

#include <cstdio>
#include <cmath>
#include <ctime>
#include <vector>
#include <set>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <string>
#include <map>

using namespace std;

#define pii pair <int, int>

int n[100], m[100];

long double ans = 1e9;
int besta, bestb, bestc, bestd;

int gcd(int a, int b)
{
	while (a != 0 && b != 0)
	{
		if (a > b)
			a %= b;
		else
			b %= a;
	}
	return a ? a : b;
}
void print(int a)
{
	int g = gcd(n[a], m[a]);
	g = 1;
	cout << n[a] / g << "/" << m[a] / g;
}

vector <int> v;

bool cmp(int a, int b)
{
	return n[a] * m[b] < n[b] * m[a];
}

bool cmp2(pii a, pii b)
{
	return (n[a.first] + n[a.second]) * (m[b.first] + m[b.second]) < (n[b.first] + n[b.second]) * (m[a.first] + m[a.second]);
}


int main()
{
	freopen("a.out", "w", stdout);
	::ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int k;
	cin >> k;
	srand(17);
	for (int i = 0; i < k; i++)
		n[i] = i + 1, m[i] = i + 1, v.push_back(i);
	random_shuffle(n, n + k);
	random_shuffle(m, m + k);
	sort(v.begin(), v.end(), cmp);
	vector <pii> vv;
	for (int a = 0; a < k; a++)
		for (int b = 0; b < k; b++)
			if (a != b)
				vv.push_back(pii(a, b));
	sort(vv.begin(), vv.end(), cmp2);
	for (auto x : vv)
	{
		print(x.first);
		cout << " + ";
		print(x.second);
		cout << endl;
	}

	for (int a = 0; a < k; a++)
		for (int b = 0; b < k; b++)
			for (int c = 0; c < k; c++)
				for (int d = 0; d < k; d++)
				{
					if (a == b || a == c || a == d) continue;
					if (b == c || b == d) continue;
					if (c == d) continue;
					if (n[a] * m[b] >= n[b] * m[a])
						if (n[c] * m[d] >= n[d] * m[c])
						{
							long double q = (n[a] + n[c]) * (m[b] + m[d]) - (n[b] + n[d]) * (m[a] + m[c]);
							q /= (m[a] + m[c]) * (m[b] + m[d]);
							if (ans > q)
							{
								ans = q;
								besta = a;
								bestb = b;
								bestc = c;
								bestd = d;
							}
						}
				}
	//for (int i = 0; i < k; i++)
	//	print(v[i]), cout << " ";
	cout << endl;
	print(besta);
	cout << " : ";
	print(bestb);
	cout << endl;
	print(bestc);
	cout << " : ";
	print(bestd);
	cout << endl;
	cout << ans;
	return 0;
}