#include <fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
struct doi
{
        int a;
        int b;
};
doi v[1003];
int n,i,s,sumcost,x,y, minsum=2000000000;
int main()
{
    int sum=0;
    fin>>n>>s;
    for(i=1;i<=n;i++)
    {
        fin>>x>>y;
        v[i].a=sum+x;
        sum=v[i].a;
        v[i].b=sumcost+y;
        sumcost=v[i].b;
        if(sum>=s)
        {
            sum=0;
            if(sumcost<minsum)
                minsum=sumcost;
            sumcost=0;
        }
        if(x>=s && minsum>y)
            minsum=y;
    }
    fout<<minsum;
    return 0;
}