#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define vi vector<int>
#define pi pair<int,int>
#define sz(v) (int)(v).size()
#define all(v) (v).begin(), (v).end()
#define compact(v) (v).erase(unique(all(v)), (v).end())
template<class T> using upq = priority_queue<T, vector<T>, greater<T>>;
template<class T> int lwrbound(const vector<T>& a, const T& b, const int s = 0){return int(lower_bound(s + all(a), b) - a.begin());}
template<class T> int uprbound(const vector<T>& a, const T& b, const int s = 0){return int(upper_bound(s + all(a), b) - a.begin());}
#define FOR(i, a, b) for(int i = (a); i <= (b); i++)
#define ROF(i, a, b) for(int i = (a); i >= (b); i--)
#define sumof(x) accumulate(all(x), 0ll)
#define dbg(x) "[" << #x " = " << (x) << "]"
#define el "\n"
using ll = long long;
using ld = long double;
template<class T> bool ckmx(T& a, const T b){return (a < b ? a = b, true : false);}
template<class T> bool ckmn(T& a, const T b){return (a > b ? a = b, true : false);}
const int N = 1e5 + 5;
const ll INF = 1e18;
struct BIT{
vector<ll> bit;
BIT(int n = 0): bit(n + 1, -INF) {}
void updPre(int p, ll val){
for(; p < sz(bit); p += p & -p){
ckmx(bit[p], val);
}
}
ll queryPre(int p){
ll ans = 0;
for(; p > 0; p -= p & -p){
ckmx(ans, bit[p]);
}
return ans;
}
void updSuf(int p, ll val){
for(; p > 0; p -= p & -p){
ckmx(bit[p], val);
}
}
ll querySuf(int p){
ll ans = -INF;
for(; p < sz(bit); p += p & -p){
ckmx(ans, bit[p]);
}
return ans;
}
};
int n, m, k, d, rec, cord[N], heal[N]; ll dp[N];
vector<int> comp;
void Main()
{
cin >> k >> m >> d >> rec >> n;
cord[0] = k, heal[0] = 0;
FOR(i, 1, n){
cin >> cord[i] >> heal[i];
}
cord[n + 1] = m, heal[n + 1] = 0;
/*
dp[j] + 1ll * (cord[j] / d) * rec
+ heal[i] - (cord[i] / d) * rec - (cord[i] % d > cord[j] % d ? rec : 0)
*/
FOR(i, 0, n + 1) comp.eb(cord[i] % d);
comp.eb(-1);
sort(all(comp)), compact(comp);
BIT pre(sz(comp)), suf(sz(comp));
FOR(i, 0, n + 1){
int p = lwrbound(comp, cord[i] % d);
if(i){
dp[i] = -INF;
ckmx(dp[i], 1ll * heal[i] - 1ll * (cord[i] / d) * rec + suf.querySuf(p));
ckmx(dp[i], 1ll * heal[i] - 1ll * (cord[i] / d + 1) * rec + pre.queryPre(p));
}
pre.updPre(p, dp[i] + 1ll * (cord[i] / d) * rec);
suf.updSuf(p, dp[i] + 1ll * (cord[i] / d) * rec);
}
cout << dp[n + 1] << el;
}
int32_t main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#define name "InvMOD"
if(fopen(name".INP", "r")){
freopen(name".INP", "r", stdin);
freopen(name".OUT", "w", stdout);
}
int t = 1; while(t--) Main();
return 0;
}
