#include <bits/stdc++.h>
using namespace std;
const int N = 100'000 + 10;
const long long MAX = 2'000'000'000'000'000'000;
int k, m, d, cost, n;
int pos[N], add[N];
int mod[N], inv[N];
long long f[N];
namespace IT {
long long f[N << 2];
void build(int s, int l, int r) {
f[s] = -MAX;
if (l == r) return;
int mid = (l + r) >> 1;
build(s << 1, l, mid); build(s << 1 | 1, mid + 1, r);
}
void update(int s, int l, int r, int p, long long x) {
if (p < l || p > r) return;
if (l == r) {
f[s] = max(f[s], x);
return;
}
int mid = (l + r) >> 1;
update(s << 1, l, mid, p, x); update(s << 1 | 1, mid + 1, r, p, x);
f[s] = max(f[s << 1], f[s << 1 | 1]);
}
long long query(int s, int l, int r, int u, int v) {
if (v < l || u > r) return -MAX;
if (u <= l && r <= v) return f[s];
int mid = (l + r) >> 1;
return max(query(s << 1, l, mid, u, v), query(s << 1 | 1, mid + 1, r, u, v));
}
}
int32_t main() {
cin.tie(0)->sync_with_stdio(0);
cin >> k >> m >> d >> cost >> n;
for (int i = 1; i <= n; ++i) cin >> pos[i] >> add[i];
pos[0] = k, pos[n + 1] = m;
vector<int> allR;
for (int i = 0; i <= n + 1; ++i) {
mod[i] = pos[i] % d;
inv[i] = pos[i] / d;
allR.push_back(mod[i]);
}
sort(allR.begin(), allR.end());
allR.erase(unique(allR.begin(), allR.end()), allR.end());
auto it = [&](int x) {
return upper_bound(allR.begin(), allR.end(), x) - allR.begin();
};
IT::build(1, 1, allR.size());
IT::update(1, 1, allR.size(), it(mod[0]), 1ll * inv[0] * cost);
fill(f + 1, f + n + 2, -MAX);
for (int i = 1; i <= n + 1; ++i) {
long long subtract = -MAX;
subtract = max(subtract, IT::query(1, 1, allR.size(), 1, it(mod[i]) - 1));
subtract = max(subtract, IT::query(1, 1, allR.size(), it(mod[i]), allR.size()) + cost);
f[i] = -1ll * inv[i] * cost - cost + subtract + add[i];
IT::update(1, 1, allR.size(), it(mod[i]), 1ll * inv[i] * cost + f[i]);
}
cout << f[n + 1] << "\n";
}
