#include<bits/stdc++.h>
using namespace std;
int m,n,x=0,y=0;
double ans;
int main()
{
    cin>>n>>m;
    for (int i = 1; i <= n; ++i) 
    {
        int a,b;
        cin >> a >> b;
        if (a == 1) 
        {
    	    x += b;
        } 
        else  y += b;
    }
    ans = ((double) m) * y / (x + y);
    printf("%.3lf\n", ans);
	return 0;
}
```//求助QwQ谢谢！