local x, y = io.read("*n", "*n")
local n = io.read("*n")
local prev = io.read("*n")
local lost = false
for i = 2, n do
  local next = io.read("*n")
  if(not lost) then
    if(next * x < prev * y) then
      lost = true
    end
    prev = next
  end
end
print(lost and "NO" or "YES")