#include <bits/stdc++.h>

#define ln                 '\n'
#define all(dat)           dat.begin(), dat.end()
#define loop(i, to)        for (int i = 0; i < to; ++i)
#define cont(i, to)        for (int i = 1; i <= to; ++i)
#define circ(i, fm, to)    for (int i = fm; i <= to; ++i)
#define foreach(i, dat)    for (__typeof(dat.begin()) i = dat.begin(); i != dat.end(); ++i)

typedef long long          num;

using namespace std;

const int nsz = 3e5;
int n, a[nsz + 5];
num ans, sum[nsz + 5];
map<num, int> cnt;

int main() {
	scanf("%d", &n);
	cont (i, n) scanf("%d", &a[i]);
	for (int i = 2; i <= n; i += 2) a[i] = -a[i];
	cnt[0] = 1;
	cont (i, n) {
		sum[i] = sum[i - 1] + a[i];
		ans += cnt[sum[i]];
		cnt[sum[i]] += 1;
	}
	printf("%lld\n", ans);
}
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

//#define ATCODER
#ifdef ATCODER
#include<atcoder/all>
using namespace atcoder;
#endif


#include <algorithm>
#include <utility>
#include <vector>



#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include <cassert>
#include <numeric>
#include <type_traits>

using namespace std;

#ifdef _MSC_VER
#include"stdafx.h"
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
	cerr << " " << (H);
	debug_out(T...);
}
#define DEBUG(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define DEBUG(...) 42
#endif

#define ll long long
#define REP(i, n) for (ll i = 0; i < (n); ++i)
#define REPR(i, n) for (ll i = (n) - 1; i >= 0; --i)
#define FOR(i, m, n) for (ll i = (m); i < (n); ++i)
#define VSORT(v) sort(v.begin(), v.end());
#define VREVERSE(v) reverse(v.begin(), v.end())

#define print(x) cout << (x) << '\n'
#define spa <<" "<<
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
#define int long long
//#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << " \n"[i==(int)v.size()-1]
template <typename T1, typename T2> inline void chmin(T1 & a, T2 b) { if (a > b) a = b; }
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 998244353;
constexpr int MAX = 300050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e17 + 1;
constexpr int INF = 1e9 + 1;


struct UnionFind {
	int N;
	vector<int> siz;
	vector<int> par;
	vector<int> Rank;
	UnionFind(int n) : siz(n, 1), par(n), Rank(n, 0) {
		N = n;
		for (int i = 0; i < N; i++) par[i] = i;
	}
	int find(int x) {
		if (par[x] == x) {
			return x;
		}
		else {
			return par[x] = find(par[x]);
		}
	}
	void unite(int x, int y) {
		x = find(x);
		y = find(y);
		if (x == y) return;
		if (Rank[x] < Rank[y]) {
			par[x] = y;
			siz[x] += siz[y];
			siz[y] = siz[x];
		}
		else {
			siz[y] += siz[x];
			siz[x] = siz[y];
			par[y] = x;
			if (Rank[x] == Rank[y]) Rank[x]++;
		}
	}
	bool same(int x, int y) { return find(x) == find(y); }
};
typedef complex<double> point;
void solve() {
	int N; cin >> N;
	//UnionFind uf(N + 2);
	vector<point>ps;
	REP(i, N) {
		int x, y; cin >> x >> y;
		ps.emplace_back(x, y);
	}
	double ans = 0;
	double ok = 0, ng = 200;
	REP(_, 50) {
		double mid = (ok + ng) / 2;
		UnionFind uf(N + 2);
		REP(i, N)FOR(j, i + 1, N) {
			if (abs(ps[i] - ps[j]) < 2 * mid)uf.unite(i, j);
		}
		REP(i, N) {
			if (abs(100 - ps[i].imag()) < 2 * mid)uf.unite(i, N);
			if (abs(-100 - ps[i].imag()) < 2 * mid)uf.unite(i, N + 1);
		}
		if (uf.same(N, N + 1))ng = mid;
		else ok = mid;
	}
	cout << setprecision(10) << fixed << ok << endl;
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	//int q; cin >> q; while (q--)
	solve();
}