/*
vector< vector<int> > Matrix(10, vector<int>(20, -1));
iterator max_element(range);
iterator min_element(range);
sort ALLR descending
string s
istringstream is(s); is >> x;
ostringstream os(s); os << x;

for (auto x : container)
{
cout << x << endl;
}

for_each(v.begin(), v.end(),
[&] (int x) {
cout << x << endl;
}
)


*/

/*
------------------------------------------------------------------
void dfs(int i) {
if (!V[i]) {
V[i] = true;
for_each(all(W[i]), dfs);
}
}

bool check_graph_connected_dfs() {
int start_vertex = 0;
V = vi(N, false);
dfs(start_vertex);
return (find(all(V), 0) == V.end());
}

void add(int poz, int val) {
for (; poz <= N; poz += zeroes(poz)) {
aib[poz] += val;
}
}

long long compute(int poz) {
long long sum = 0;
for (; poz; poz -= zeroes(poz)) {
sum += aib[poz];
}
return sum;
}
*/

#include <fstream>
#include <iostream>
#include <string>
#include <complex>
#include <cmath>
#include <set>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <stack>
#include <algorithm>
#include <list>
#include <ctime>
#include <cassert>
#include <iomanip>

using namespace std;

//```
#define ONLINE_JUDGE1

const double epsilon = 1e-7;
#define LL long long
#define ULL unsigned long long 

typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<string> vs;
typedef pair<int, int> ii;
typedef pair<long long, long long> ll;
typedef vector<ii> vii;
typedef vector<ll> vll;

#define all(V) V.begin(), V.end()
#define allr(V) V.rbegin(), V.rend()
#define for_c_it(container, it) for (auto it = container.begin(); it != container.end(); it++)
#define present(container, element) (container.find(element) != container.end()) 
#define sz(a) int((a).size()) 
#define pb push_back 
#define mp make_pair
#define zeroes(x) ((x ^ (x - 1)) & x)

int N;
vector<double> Vx, Vy;

double function(double a, double b, double val) {
	return b*val + a;
}

int main() {
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
#endif
	double A, B, auxA, auxB;
	double alpha = 0.0001, sum;
	A = B = 0;
	cin >> N;
	Vx.resize(N);
	Vy.resize(N);
	for (int i = 0; i < N; ++i) {
		cin >> Vx[i] >> Vy[i];
	}
	int step = 1000;
	while (step--) {
		sum = 0;
		for (int i = 0; i < N; ++i) {
			sum += function(A, B, Vx[i]) - Vy[i];
		}
		auxA = A - alpha * (1 / (double)N) * sum;
		sum = 0;
		for (int i = 0; i < N; ++i) {
			sum += (function(A, B, Vx[i]) - Vy[i]) * Vx[i];
		}
		auxB = B - alpha * (1 / (double)N) * sum;
		if (fabs(A - auxA) < 0.0001 && fabs(B - auxB) < 0.0001) break;
		A = auxA;
		B = auxB;
	}
	sum = 0;
	for (int i = 0; i < N; ++i) {
		sum += (Vy[i] - function(A, B, Vx[i])) * (Vy[i] - function(A, B, Vx[i]));
	}
	printf("%.5lf", sum);
	while (1);
	return 0;
}