#include<bits/stdc++.h>
#define int   long long
#define ll long long
#define down cout<<'\n';
#define debug cout<<" cucuucucuuu",down
#define NHP     ios_base::sync_with_stdio(0);cout.tie(0);cin.tie(0);
#define modwwe  int t;cin>>t; while(t--)
#define bit(i,j) (i>>j&1)
#define sobit(a) __builtin_popcountll(a)
#define task "test"
#define fin(x) freopen(x".inp","r",stdin)
#define fou(x) freopen(x".out","w",stdout)
#define pb push_back
#define mask(k) (1<<k)
#define mp make_pair
#define checktime   cerr << (double)clock() / CLOCKS_PER_SEC * 1000  << " ms";
using namespace std;
#define getchar_unlocked getchar

inline int scan()
{
    char c = getchar_unlocked();
    int x = 0;
    while (c < '0' || c > '9')
    {
        c = getchar_unlocked();
    }
    while (c >= '0' && c <= '9')
    {
        x = (x << 1) + (x << 3) + c - '0';
        c = getchar_unlocked();
    }
    return x;
}
void phongbeo();
const int inf = 2e18;
const ll mod2 = 998244353;
const int  mod1 = 998244353;
const ll base=67;
int add(int x,int y)
{
    if(x+y>=mod2) x-=mod2;
    if(x+y<0)x+=mod2;
    return x+y;
}
struct icd
{
    long double a;
    int b;
};
struct ib
{
    int a;
    int b;
};
struct ic
{
    int a, b, c;
};
struct id
{
    int a, b, c, d;
};
struct ie
{
    int a, b, c, d, e;

};
int n, m, s1, s2, s4, s3, sf, k, s5, s6, mx, s7, s8, s9, mx2, res, dem2 = 0, dem = 0, s33, dem3, dem4, mid, l2, r2, center;
int  i, s10, s12,k1,k2,k3,s11,lim,w,l,r,ans ;
int kk;
int el = 19;
main()
{
    if(fopen(task".inp","r"))
    {
        fin(task);
        fou(task);
    }
    NHP
    /// cin>>s1;
    //modwwe
    phongbeo(),down
    // checktime
}
int t[400010];
int pos[100010];
int money[100010];
int f[100010];
int dp[100010];
int cost;
vector<int> v;
void upd(int node,int l,int r,int l1,int x)
{
    if(l==r)
    {
        t[node]=max(t[node],x);
        return;
    }
    int mid=l+r>>1;
    if(l1<=mid)
        upd(node<<1,l,mid,l1,x);
    else upd(node<<1|1,mid+1,r,l1,x);
    t[node]=max(t[node<<1],t[node<<1|1]);
}
int get(int node,int l,int r,int l1,int r1)
{
    if(l>r1||r<l1||t[node]==-inf) return -inf;
    if(l>=l1&&r<=r1) return t[node];
    int mid=l+r>>1;
    return max(get(node<<1,l,mid,l1,r1),get(node<<1|1,mid+1,r,l1,r1));
}
/// 12 -1
/// 21 -11
/// 26 -21
void phongbeo()
{
    cin>>pos[0]>>m>>lim>>cost>>n;
    for(int i=1; i<=n; i++)
        cin>>pos[i]>>money[i];
    pos[++n]=m;
    for(int i=0; i<=n; i++)
        v.pb(pos[i]%lim),f[i]=pos[i]/lim;
    sort(v.begin(),v.end());
    v.erase(unique(v.begin(),v.end()),v.end());
    for(int i=0; i<=n; i++)
        pos[i]=lower_bound(v.begin(),v.end(),pos[i]%lim)-v.begin()+1;
    k=v.size();
    upd(1,1,k,pos[0],f[0]*cost);
    for(int i=1; i<=n; i++)
    {
        s2=get(1,1,k,pos[i],k)-f[i]*cost;
        s3=(get(1,1,k,1,pos[i]-1))-f[i]*cost-cost;
        s2=max(s2,s3);
        dp[i]=s2+money[i];
        upd(1,1,k,pos[i],dp[i]+f[i]*cost);
    }
    cout<<dp[n];
}