#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".ans","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();
for(int i=1;i<=4*k;i++)
t[i]=-inf;
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];
}
