#include <iostream>
#include <algorithm>
using namespace std;
int n,t;
double sum;
struct node
{
int m,v;
double dv;
}a[114];
bool cmp(node n1,node n2)
{
return n1.dv > n2.dv;
}
int main() {
cin>>n>>t;
for(int i = 1;i <= n;i++)
{
cin>>a[i].m>>a[i].v;
a[i].dv = 1.00*a[i].v / a[i].m;
}
sort(a + 1,a + n + 1,cmp);
for(int i = 1;i <= n;i++)
{
if(t > a[i].m)
{
sum += a[i].v;
t -= a[i].m;
}
else
{
sum += t * a[i].dv;
break;
}
}
printf("%.2lf",sum);
return 0;
}