import std.algorithm, std.conv, std.range, std.stdio, std.string;

void main()
{
  auto rd = readln.split.to!(int[]), x = rd[0], y = rd[1];
  auto n = readln.chomp.to!size_t;
  auto ai = readln.split.to!(real[]);

  auto txi = ai.map!(a => a / x).array;
  auto tyi = ai.map!(a => a / y).array;

  auto si = tyi[1..$];
  si[] -= txi[0..$-1];

  writeln(si.all!"a >= 0" ? "YES" : "NO");
}