#include <iostream>
#include <iomanip>
#include <vector>
#include <utility>
#include <algorithm>

int main(){
    int n, t = 0, w;
    long long v = 0;
    std::cin >> n >> w;
    std::vector<std::pair<int, int>> ms(n);
    for (std::pair<int, int> &m : ms) std::cin >> m.second >> m.first;
    std::sort(ms.begin(), ms.end());
    for (std::pair<int, int> &m : ms){
        if (v > 0 && 2*m.first-t > (w-1)/v) break;
        w -= v*(2*m.first-t);
        t = 2*m.first;
        v += m.second;
    }
    std::cout << std::setprecision(13) << t+(long double)w/v << std::endl;
    return 0;
}