#include <iostream>

using namespace std;

int main()
{
    int n;
    double v, l;
    cin >> n >> v >> l;
    l *= 60;
    l /= v;
    for (int i = 0; i < n; ++i)
    {
        double a, b;
        cin >> a >> b;
        l += b;
    }
    cout.precision(2);
    cout << fixed << l;
}