Rucsac

#include <iostream>
#include <algorith>

using namespace std;

//ifstream cin(".in");
//ofstream cout(".out");

struct obc
{
    float G, V;
} v[1005];

bool cond(obc i, obc j)
{
    if(i.V / i.G > j.V / j.G) return true;
    else return false;
}

int main()
{
    int n, GM;

    cin >> n >> GM;

    for(int i = 1; i <= n; ++i)
    {
        cin >> v[i].G >> v[i].V;
    }

    sort(v + 1, v + n + 1, cond);

    double S = 0, GR = 0;

    for(int i = 1; i <= n and GR <= GM; ++i)
    {
        if(GR + v[i].G <= GM)
        {
            GR += v[i].G;
            S += v[i].V;
        }
        else
        {
            double r = GM - GR, j = v[i].V / v[i].G;
            S += r * j;
            break;
        }
    }

    cout << S;

    return 0;
}