#include <stdio.h>
#include <stdlib.h>

int max ( int *t, long *p, int n,long c,long cunic) {
    long * cost;
    cost = ( long * ) malloc ( (n+1) * sizeof(long));
    if (p[0]>cunic) cost [0] = cunic - c; else cost [0] =-c;
    int i;
    for ( i = 1; i<n; i++)
     if ( p[i] < cunic ) cost [i] = cost [i-1] - c*(t[i]-t[i-1]);
       else 
        {   cost[i]=cunic-c; 
            if ( cost [i-1] - c * (t[i]-t[i-1]-1)  > 0)
               cost[i]+= cost [i-1] - c * (t[i]-t[i-1]-1) ;
               }
    long maxim=0;
    for (i=0;i<n;i++) if (maxim<cost[i]) maxim=cost[i];
    return maxim;
}

int main() {
    FILE *f=fopen("carnati.in","r");
    int n,i;long c;
    long *p;int *t;
    fscanf(f,"%d%ld\n",&n,&c);
    p = ( long * ) malloc ( sizeof(long) * (n+1));
    t = ( int * ) malloc ( sizeof(int) * (n+1));
    for ( i=0; i<n;i++) fscanf(f,"%d%ld\n",t+i,p+i);
    long maximul=0,total;
        for (i=0;i<n;i++)
      {
        total = max ( t,p,n,c,p[i]);
        printf("%ld\n",total);
        if (total > maximul) maximul=total;
        }
      fclose(f);
      f=fopen("carnati.out","w");
      fprintf(f,"%ld",maximul);
      fclose(f);
    return 0;
}