#include <iostream>
#include <math.h>

using namespace std;

int main()
{
    int i,j,l;
	int k;          // Numbers.
	double a[30];    // Each number is in the range 0 < a[i] < 10^7.
	double subtrahend;
	double a1,a2,a3;
	int flag;
	cin >> k;
	while(k > 0)
	{
		flag = 0;
		cin >> a[0];
		if(k == 1)
		{
			cout << "NO" << endl;
		}
		else 
		{
			for (i=1; i<k; i++)
			{
				cin >> a[i];
			}
			for(i=0; i<k-1; i++)
			{
				for(j=i+1; j<k; j++)
				{
					subtrahend = fabs(a[i] - a[j]);
					if(subtrahend < 1e-6) 
					{
						cout << "YES" << endl;
						flag = 1;
						break;
					}
					else
					{
						for(l=0; l<k; l++)
						{
							if(l!=i && l!=j)
							{
								if(subtrahend-a[l] < 1e-6)
								{
									a1 = a[i];
									a2 = a[j];
									a3 = a[l];
									if(a1 > a2)
									{
										a1 = a[j];
										a2 = a[i];
									}
									if(a2 > a3)
									{
										a3 = a2;
										a2 = a[l];
									}
									if(a3-a1-a2 < 1e-6)
									{
										cout << "YES" << endl;
										flag = 1;
										break;
									}
								}
							}
						}
					}
					if(flag > 0) break;
				}
				if(flag > 0) break;
			}
			if(flag == 0) cout << "NO" << endl;
		}
		cin >> k;
	}
    return 0;
}

• ac now！！！ (37) hua0629 2005-10-07 19:39:18