#include<iostream>
#include<string>
#include<stdlib.h>
#include<fstream>
#include <time.h> 
#include <algorithm>

using namespace std;

int main()
{
    ifstream in("energii.in");
    ofstream of("energii.out");
	int g,w,i,a[100][100],min=10000;
	
	in>>g>>w;
	for(i=1;i<=g;i++)
		{
		in>>a[i][1]>>a[i][2];
		if(w%a[i][1]==0)
			a[i][3]=(w/a[i][1])*a[i][2];
		else
			a[i][3]=((w/a[i][1])+1)*a[i][2];
		}
	for(i=1;i<=g;i++)
		if(a[i][3]<min)
			min=a[i][3];
			
//cout<<min;
	of<<min;

	
	in.close();
	of.close();
}