#include<bits/stdc++.h>
using namespace std;
struct coin{
    int v;
    int m;
	double c;
}a[101];
double sum=0;
int n,t;
bool cmp(coin x,coin y){
    return x.c>y.c;
}
int main(){
    cin>>n>>t;
    for (int i=0;i<n;i++){
        cin>>a[i].m>>a[i].v;
        a[i].c=a[i].v/a[i].m;
    }
    sort(a,a+n,cmp);
    for (int i=0;i<n;i++){
        if (a[i].c>=t){
            a[i].c-=t;
            sum+=t;
        }else{
            sum+=a[i].c-t;
            break;
        }
    }
    cout<<fixed<<setprecision(2)<<sum;
    return 0;
}