import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;


public class polygon {
	
	public static void main(String[] args) throws Exception
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		
		while(true)
		{
			String s = in.readLine();
			if(s.equals("0"))
				break;
			int[] useckyX = new int[Integer.valueOf(s)];
			int[] useckyY = new int[Integer.valueOf(s)];
			for(int i=0; i<useckyX.length; i++)
			{
				s = in.readLine();
				String ss[] = s.split(" ");
				useckyX[i] = Integer.valueOf(ss[0]);
				useckyY[i] = Integer.valueOf(ss[1]);
			}
			//System.out.println(Arrays.toString(usecky));
			
			double koefA[] = new double[useckyX.length];
			double koefB[] = new double[useckyX.length];
			double koefC[] = new double[useckyX.length];
			for(int i=0, j = 0; i<useckyX.length; i++)
			{
				j = (i+1)%useckyY.length;
				koefA[i] = useckyY[i] - useckyY[j];
				koefB[i] = useckyX[j] - useckyX[i];
				koefC[i] = useckyX[i]*useckyY[j] - useckyX[j]*useckyY[i];
			}
			//System.out.println(Arrays.toString(koefA));
			//System.out.println(Arrays.toString(koefB));
			//System.out.println(Arrays.toString(koefC));
			
			boolean prusecik = false;
			for(int i=1; i<koefA.length; i++)
			{
				for(int k=i+1, j = 0; k<koefA.length + 1; k++)
				{
					j = k % koefA.length;
					double x = koefB[i] * koefC[j] - koefC[i] * koefB[j];
					double y = koefC[i] * koefA[j] - koefA[i] * koefC[j];
					double w = koefA[i] * koefB[j] - koefB[i] * koefA[j];
					//todo
					if(w==0)
					{
						if (Math.abs(koefA[i] * useckyX[j] + koefB[i] * useckyY[j] + koefC[i]) < 0.0001)
						{
							prusecik = true;
							break;
						}
						else continue;
					}
					x /= w; 
					y /= w; 
					//System.out.println(x+" "+y+" "+w+"    "+useckyX[i]+" "+useckyY[i]+"   "+useckyX[j]+" "+useckyY[j]+"   "+x+" "+y);
					double x1 = useckyX[i];
					double x2 = useckyX[(i+1)%useckyX.length];
					if(x1>x2)
					{
						double pom = x1;
						x1 = x2;
						x2 = pom;
					}
						if(x<=x2 && x>=x1 && (j > i+1))
						{
							x1 = useckyX[j];
							x2 = useckyX[(j+1)%useckyX.length];
							if(x1>x2)
							{
								double pom = x1;
								x1 = x2;
								x2 = pom;
							}
							if(x<=x2 && x>=x1 && (j > i+1))
							{
								prusecik = true;
								break;
							}
						}
				}
			}
			if(!prusecik)
				System.out.println("YES");
			else
				System.out.println("NO");
		}
	}

}