import std.stdio, std.algorithm, std.array, std.conv, std.typecons;

alias Set = bool[3 * 10^^5];

void main() {
	readln;
	auto A = readln.split.to!(long[]);
	
	foreach (a; A) {
		if (a < 0) {
			writeln("No");
			return;
		}
		else if (a > 0) {
			writeln("Yes");
			return;
		}
	}
	
	writeln("No");
}