#include <fstream>
#include <algorithm>

using namespace std;
int main()
{
    ifstream cin("carnati.in");
    ofstream cout("carnati.out");
    int n,c,t,p,nrc,profm=-1,inc,sfaf,sfa,incf,i,contor;
    cin>>n>>c;
    inc=1;
    nrc=0;
    sfa=0;
    incf=1;
    for(i=1;i<=n;i++){
        cin>>t>>p;
        sfa=t;
        if(nrc*129-(sfa-incf+1)*c<=0){
            inc=t;
            nrc=0;
        }
        if(p>=129)
            nrc++;
        if(nrc*129-(sfa-incf+1)*c>profm){
            sfaf=t;
            incf=inc;
            profm=nrc*129-(sfa-incf+1)*c;
        }
    }
    cout<<profm;
    return 0;
}