//*******************************
//???????????????
//?????
//???2011-11-7
//*******************************
int main()
{
	char a[100000];              //???????
	char b[27] = {"abcdefghijklmnopqrstuvwxyz"};        //???????????
	int c[100000];                        //???????????????
	int i, j, x, y = 0, min, t, k, first = 1, count = 0;           //??????
	cin >> t;                     //??????
	for(k = 1;k <= t;k++)              
	{
		for(i = 0;i <= 99999;i++)            //?c?????
			c[i] = 100000;
		y = 0;               //?y???
		if(first == 1)          //????????????
		{ 
			cin.get();
			first = 0;
		}
		cin.getline(a, 100000);            //?????
		for(i = 0;b[i] != '\0';i++)            
		{
			count = 0;               //?????????
			for(j = 0;a[j] != '\0';j++)
			{
				if(b[i] == a[j])           //??????????26??????????????????
				{
					x = j;              //?????????????
					count++;        //????????
				}
			}
			if(count == 1)          //???????????????c???
			{
				c[y] = x;
				y++;
			}
		}
		if(c[0] == 100000)           //?c[0] = 100?????????????
		{
			cout << "no" << endl;
		}
		else
		{
			min = c[0];                //?c[0]????
			for(i = 1;i <= 99999;i++)      //?????
			{
				if(min > c[i])
				{
					min = c[i];         
				}
			}                          
			cout << a[min] << endl;      //??????a????????
		}
	}
	return 0;
}