waterfront

#include <bits/stdc++.h>

using namespace std;
const int N = 10005;
const int Mask=(1<<14)-1;
int n,m,k,x,h[N],g[N],H[N],v[N],d[N],t[N],c[Mask+1],top,bottom;
int cuts;
bool crit(int,int);
void readAndInit(),taie();
int main()
{
    readAndInit();
    while(1)
        taie();
    return 0;
}
/// criteriu de sortare
bool crit(int i,int j)
{
    return H[i]<H[j];
}
/// citire si initializare

void readAndInit()
{
    cin>>n>>m>>k>>x;
    for(int i=1;i<=n;i++)
    {
        cin>>h[i]>>g[i];
        H[i]=h[i]+m*g[i];
        v[i]=i;
    }
    for(int i=1;i<=m;i++)
        t[i]=k;
    cuts=m*k;
    t[m+1]=1;
    sort(v+1,v+n+1,crit);
    c[0]=v[n--];
    top=bottom=0;
}
void taie()
{
    int co=c[bottom];bottom=(bottom+1)&Mask;
    if(h[co]<x)
    {
        int days=(x-h[co])/g[co];
        if((x-h[co])%g[co]) days++;
        if(d[co]+days>m)
        {
            cout<<H[co]<<'\n';
            exit(0);
        }
        d[co]+=days;
        h[co]+=days*g[co];
    }
    while(!t[d[co]]){d[co]++;h[co]+=g[co];}
    if(d[co]==m+1)
    {
        cout<<H[co]<<'\n';
        exit(0);
    }
    H[co]-=x;
    h[co]-=x;
    t[d[co]]--;
    cuts--;
    while(n>0&&H[v[n]]>=H[co])
    {
        top=(top+1)&Mask;
        c[top]=v[n];
        n--;
    }
    top=(top+1)&Mask;
    c[top]=co;
}