675 B | 675 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
while 1:
l = mii()
n, width, length, height, area, m = l
if sum(l) == 0:
break
l = [mii() for _ in range(m)]
k = (width + length) * height * 2 + (width * length)
for a, b in l:
k -= a * b
k *= n
print(k // area + int(k % area > 0))
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
solve()