#include <bits/stdc++.h>
#pragma comment(linker, "/stack:225450978")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
const long long Mod = 1000000007LL, INF = 1e9, LINF = 1e18;
const long double Pi = 3.141592653589793116, EPS = 1e-9,
                  Gold = ((1 + sqrt(5)) / 2);
long long keymod[] = {1000000007LL, 1000000009LL, 1000000021LL, 1000000033LL};
long long keyCount = sizeof(keymod) / sizeof(long long);
template <class T>
int getbit(T s, int i) {
  return (s >> i) & 1;
}
template <class T>
T onbit(T s, int i) {
  return s | (T(1) << i);
}
template <class T>
T offbit(T s, int i) {
  return s & (~(T(1) << i));
}
template <class T>
int cntbit(T s) {
  return __builtin_popcountll(s);
}
auto TimeStart = chrono::steady_clock::now();
auto TimeEnd = chrono::steady_clock::now();
void ControlIO(int argc, char* argv[]);
void TimerStart();
void TimerStop();
void Exit();
long long n, m, xc, yc, k;
vector<pair<long long, long long> > d;
void Input() {
  cin >> n >> m >> xc >> yc >> k;
  d.resize(k);
  for (long long i = 0; i < k; i++) cin >> d[i].first >> d[i].second;
}
void Solve() {
  long long ans = 0;
  for (auto z : d) {
    long long x = z.first, y = z.second;
    long long cntx = LINF, cnty = LINF;
    if (x < 0)
      cntx = (xc - 1) / (-x);
    else if (x > 0)
      cntx = (n - xc) / (+x);
    if (y < 0)
      cnty = (yc - 1) / (-y);
    else if (y > 0)
      cnty = (m - yc) / (+y);
    long long steps = min(cntx, cnty);
    xc += steps * x;
    yc += steps * y;
    ans += steps;
  }
  cout << ans;
}
int main(int argc, char* argv[]) {
  ControlIO(argc, argv);
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  Input();
  TimerStart();
  Solve();
  TimerStop();
  return 0;
}
void ControlIO(int argc, char* argv[]) {}
void TimerStart() {}
void TimerStop() {}
void Exit() {
  TimerStop();
  exit(0);
}
