#include <cstdio>
#include <algorithm>
#include <vector>
#define INF 2000000000
#define DIMN 30010
using namespace std;
int d[6][DIMN];

vector <int> v[DIMN];
int main()
{
    FILE *fin=fopen ("magazin.in","r");
    FILE *fout=fopen ("magazin.out","w");
    int p,n,m,dst,x,y,up,down,mini,i,j;
    fscanf (fin,"%d%d%d%d",&p,&n,&m,&dst);
    for (i=1;i<=p;i++){
        fscanf (fin,"%d%d",&x,&y);
        v[x].push_back(y);
    }


    for (i=1;i<=n;i++){

        up = down = mini = 0;

        if (v[i].size()){ /// sunt cateva produse aici
            sort (v[i].begin() , v[i].end());
            up = v[i][v[i].size()-1];
            down = m+1 - v[i][0];
            mini = min (up,down);
            for (j = 0; j<v[i].size()-1 ; j++){
                mini = min (mini, v[i][j] + m+1 - v[i][j + 1]);
            }
            up*=2;
            down*=2;
            mini*=2;
        }

        d[0][i] = d[1][i] = d[2][i] = d[3][i] = d[4][i] = d[5][i] = INF;


        if (i==1){
            d[3][i] = up;
            d[4][i] = m+1;
            d[5][i] = mini;
        }

        else {

            d[0][i] = min (d[0][i] , dst + min (d[0][i-1] + down , d[4][i-1] + down));

            d[1][i] = min (d[1][i] , min (  min ( d[0][i-1] + dst + m+1, d[2][i-1] + 3*dst + m+1) ,
                    min( d[4][i-1] +dst + m+1, d[1][i-1] + 3*dst + mini )  ));

            d[2][i] = min (d[2][i] , min( d[0][i-1] + dst + mini , d[2][i-1] + 3*dst + mini));

            /// -----------------------------------------------------------------------

            d[3][i] = min (d[3][i] , dst + min ( d[3][i-1] + up , d[1][i-1] + up ));

            d[4][i] = min (d[4][i] , min ( min (d[3][i-1] + dst + m+1, d[5][i-1] + dst * 3 + m+1) ,
                    min ( d[4][i-1] + mini + 3* dst , d[1][i-1] + dst + m+1  )));

            d[5][i] = min ( d[5][i] , min ( d[3][i-1] + dst + mini , d[5][i-1] + 3 * dst + mini ));
        }
        //for (j=0;j<6;j++){
          //  printf ("%d ",d[i][j]);
        //}
        //printf ("\n");


    }
    fprintf (fout,"%d" , min (d[3][n] , d[1][n]));
    return 0;
}