unsigned long n;

std::vector<std::pair<unsigned long, long>> v;

std::cin >> n;

for (unsigned long i = 0; i < n; i++) {

unsigned long t;

long p;

std::cin >> t >> p;

v.push_back(std::make_pair(t, p));

}

std::sort(v.begin(), v.end(), [](const auto& a, const auto& b) {

return a.first < b.first;

});

double max_v = 0;

for (unsigned long i = 0; i < n - 1; i++) {

double velocity

= std::abs(((double)v[i + 1].second - v[i].second) / (v[i + 1].first - v[i].first));

max_v = (velocity > max_v) ? velocity : max_v;

}

std::cout << std::fixed << max_v << std::endl;