#include<fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
unsigned g,c,gen[5001],cost[1001],ig,ic,m;
int cmin()
{ unsigned min;

	for(unsigned i=0;i<g;i++)
       if(gen[i]==c&&cost[i]==m)
		  min=cost[i];
    
 return min;
}
int main()
{ fin>>g;
  fin>>c;
  for(unsigned i=0;i<g;i++)
	{  fin>>gen[ig++];
       fin>>cost[ic++]; 
	}
	for(unsigned i=0;i<g;i++)
	while(cost[i]<c)
	{ cost[i]+=cost[i];
	  gen[i]+=gen[i];
	}
	m=cost[0];
	for(unsigned i=0;i<g;i++)
		if(cost[i]<m&&gen[i]==c)
			m=cost[i];
		
    /*for(unsigned i=0;i<g;i++)
	{  fout<<gen[i]<<" ";
       fout<<cost[i]<<"\n"; 
	}*/
	fout<<cmin();
}