#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define MASK(i) (1ULL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
#define ALL(v) (v).begin(), (v).end()
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll gcd(ll a, ll b){return __gcd(a, b);}
ll lcm(ll a, ll b){return a / gcd(a, b) * b;}
ll LASTBIT(ll mask){return (mask) & (-mask);}
int pop_cnt(ull mask){return __builtin_popcountll(mask);}
int ctz(ull mask){return __builtin_ctzll(mask);}
int logOf(ull mask){return 63 - __builtin_clzll(mask);}
// mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
mt19937_64 rng(1);
ll rngesus(ll l, ll r){return l + (ull) rng() % (r - l + 1);}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b) {a = b; return true;}
return false;
}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b) {a = b; return true;}
return false;
}
template <class T>
void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
for(auto item: container) out << item << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const ll INF = 1e18 + 69;
struct SegmentTree{
struct Node{
ll val, lazy;
Node(ll val, ll lazy): val(val), lazy(lazy){}
};
int n;
vector<Node> a;
SegmentTree(int _n){
n = _n;
a.resize(n * 4 + 4, Node(0, 0));
}
void apply_node(int id, ll val){
a[id].val += val;
a[id].lazy += val;
}
void down(int id){
apply_node(id * 2, a[id].lazy);
apply_node(id * 2 + 1, a[id].lazy);
a[id].lazy = 0;
}
void update(int u, int v, ll w, int l, int r, int id){
if (u <= l && r <= v) {
apply_node(id, w);
return;
}
if (a[id].lazy) down(id);
int mid = (l + r) >> 1;
if (u <= mid) update(u, v, w, l, mid, id * 2);
if (v > mid) update(u, v, w, mid + 1, r, id * 2 + 1);
a[id].val = min(a[id * 2].val, a[id * 2 + 1].val);
}
void update(int u, int v, ll w){
maximize(u, 0); minimize(v, n-1);
if (u <= v) update(u, v, w, 0, n-1, 1);
}
void assign(int i, ll w, int l, int r, int id){
if (l == r) {
minimize(a[id].val, w);
return;
}
if (a[id].lazy) down(id);
int mid = (l + r) >> 1;
if (i <= mid) assign(i, w, l, mid, id * 2);
if (i > mid) assign(i, w, mid + 1, r, id * 2 + 1);
a[id].val = min(a[id * 2].val, a[id * 2 + 1].val);
}
void assign(int i, ll w){
assign(i, w, 0, n-1, 1);
}
ll get(int u,int v, int l, int r, int id){
if (u <= l && r <= v) return a[id].val;
if (a[id].lazy) down(id);
int mid = (l + r) >> 1;
ll ans = INF;
if (u <= mid) minimize(ans, get(u, v, l, mid, id * 2));
if (v > mid) minimize(ans, get(u, v, mid + 1, r, id * 2 + 1));
return ans;
}
ll get(int l, int r){
if (l > r) return INF;
return get(l, r, 0, n-1, 1);
}
};
void solve(){
int K, M, D, A, n;
cin >> K >> M >> D >> A >> n;
vector<ll> a(n+2), c(n+2);
a[0] = K;
for(int i = 1; i <= n; ++i) cin >> a[i] >> c[i];
a[n+1] = M;
for(auto &i: a) i -= K;
M -= K; K -= K;
vector<ll> b = a;
for(ll &i: b) i = i % D;
remove_dup(b);
int m = b.size();
SegmentTree st(m);
st.update(0, m-1, INF);
st.assign(0, 0);
for(int i = 1; i<=n+1; ++i){
int idx = lower_bound(ALL(b), a[i] % D) - b.begin();
ll dist = a[i] - a[i-1];
ll cnt = dist / D;
st.update(0, m-1, cnt * A);
if (dist % D != 0){
ll amount = dist % D;
ll l = a[i] % D - amount + 1;
ll r = a[i] % D;
for(int t = 0; t <= 1; ++t){
int idx1 = lower_bound(ALL(b), l) - b.begin(), idx2 = upper_bound(ALL(b), r) - b.begin() - 1;
st.update(idx1, idx2, A);
l += D; r += D;
}
}
ll cur = INF;
minimize(cur, st.get(0, m-1));
minimize(cur, st.get(idx, idx) - A);
cur = cur + A - c[i];
st.assign(idx, cur);
if (i == n+1) cout << st.get(idx, idx) << "\n";
// cout << st.get(0, m-1) << "\n";
}
// cout << st.get(0, m-1) << "\n";
}
int main(void){
ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);
clock_t start = clock();
solve();
cerr << "Time elapsed: " << clock() - start << " ms\n";
return 0;
}
