#include <bits/stdc++.h>
using namespace std;
long long int to_reach(long long int number, long long int moves,
                       long long int target) {
  if (target == 0) {
    return (number / moves);
  } else {
    long long int res = (target - number) / moves;
    return res;
  }
}
int main() {
  long long int n, m, xc, yc, dxi, dyi, step;
  cin >> n >> m;
  cin >> xc >> yc;
  long long int k, count = 0;
  cin >> k;
  for (int i = 0; i < k; i++) {
    cin >> dxi >> dyi;
    long long int toReachX, toReachY;
    if (dxi == 0)
      toReachX = 10000000000;
    else if (dxi > 0)
      toReachX = to_reach(xc, dxi, n);
    else
      toReachX = to_reach(1 - xc, dxi, 0);
    if (dyi == 0)
      toReachY = 10000000000;
    else if (dyi > 0)
      toReachY = to_reach(yc, dyi, m);
    else
      toReachY = to_reach(1 - yc, dyi, 0);
    long long int tomove = min(toReachX, toReachY);
    xc = xc + dxi * tomove, yc = yc + dyi * tomove;
    count += tomove;
  }
  cout << count << endl;
  return 0;
}
