看看我的，同是天涯沦落人。。。你现在A了没？

#include <cstdio>
#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
#define M 400
#define eps 1e-8
struct Point
{
	double x;
	double y;
}point[M];
char str[M];

void build()
{
	int t = 20;
	int cot = 0;
	for(int i=1;i<=20;i++)
	{
		int h = i-1;
		for(int j=1;j<=i;j++)
		{
			point[cot].x = ((double)h*sqrt(3));
			point[cot].y = ((double)2*(j-1)-h);
			cot++;
		}
	}
}

double getDis(Point a,Point b)
{
	return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y);
}
int main()
{
	int n;
	build();
	while(scanf("%d",&n) && n)
	{
		vector<char> ans;
		scanf("%s",str);
		for(int i=0;str[i];i++)	
		{
			int t1 = i,t2,t3;
			for(int j=i+1;str[j];j++)
				if(str[j] == str[i])
				{
					t2 = j;
					for( int k=j+1;str[k];k++)
						if(str[k] == str[i])
						{
							t3 = k;
						//	cout<<str[t1]<<t1<<" "<<t2<<" "<<t3<<endl;
						//	cout<<point[t1].x<<" "<<point[t1].y<<endl;
						//	cout<<point[t2].x<<" "<<point[t2].y<<endl;
						//	cout<<point[t3].x<<" "<<point[t3].y<<endl;
							if(fabs(getDis(point[t1],point[t2])-getDis(point[t2],point[t3]))<eps &&
									fabs(getDis(point[t1],point[t3])-getDis(point[t1],point[t2])<eps))
								ans.push_back(str[t1]);
						}
				}
		}
		
		if(ans.size() == 0)
			printf("LOOOOOOOOSER!\n");
		else
		{
			bool mark[27];
			memset(mark,0,sizeof(mark));
			sort(ans.begin(),ans.begin()+ans.size());
			for(int i=0;i<ans.size();i++)
			{
				if(!mark[ans[i]-'a'] )
				{
					printf("%c",ans[i]);
					mark[ans[i]-'a'] = true;
				}
			}
			cout<<endl;
		}
	}
	return 0;
}