import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

public class Main
{
	public static final int countMax = 30;


	public static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

	public static void main(String[] args) throws NumberFormatException, IOException
	{
		// TODO 自動生成されたメソッド・スタブ
		int a = Integer.parseInt(input(1)[0]);
		Map<String, Boolean> map = new HashMap<>();
		for(int i = 0; i < a; i++)
		{
			String[] str = input(2);
			if(str[0].equals("insert")) map.put(str[1], true);
			else
			{
				try
				{
					if(map.get(str[1])) System.out.println("yes");
				}
				catch(NullPointerException e)
				{
					System.out.println("no");
				}
			}
		}
	}

	public static int loop(int num, int sum, int max, boolean[] b, int now, int upper)
	{
		int a = num;
		if(max == now)
		{
			int c = 0;
			for(int i = 0; i < 10; i++)
			{
				if(b[i]) c += i;
			}
			for(int i = upper; i < 10; i++)
			{
				if(b[i]) continue;
				if(c + i == sum)
				{
					//System.err.println(sum + " " + c + " " + i);
					a++;
				}
			}
		}
		else
		{
			for(int i = upper; i < 10; i++)
			{
				if(b[i]) continue;
				b[i] = true;
				a = loop(a, sum, max, b, now + 1, i);
				b[i] = false;
			}
		}
		return a;
	}

	public static int[] toIntArray(int a)
	{
		int b[] = new int[8];
		for(int i = 0; i < 8; i++)
		{
			b[i] = (a >> (i * 3) & 0b111);
		}
		return b;
	}

	public static int toInt(int[] a)
	{
		int b = 0;
		for(int i = a.length - 1; i >= 0; i--)
		{
			b = b << 3;
			b+=a[i];
		}
		return b;
	}

	public static int toInt(Integer[] a)
	{
		int b = 0;
		for(int i = a.length - 1; i >= 0; i--)
		{
			b = b << 3;
			b+=a[i];
		}
		return b;
	}

	static void QuickSort(int[] d, int left, int right) {
		if (left>=right) {
			return;
		}
		int p = d[(left+right)/2];
		int l = left, r = right, tmp;
		while(l<=r) {
			while(d[l] < p) { l++; }
			while(d[r] > p) { r--; }
			if (l<=r) {
				tmp = d[l]; d[l] = d[r]; d[r] = tmp;
				l++; r--;
			}
		}
		QuickSort(d, left, r);
		QuickSort(d, l, right);
    }

	public static boolean SeparateSearch(int[] a, int b, int first, int end)
	{
		if(end - first <= 1)
		{
			if(a[first] == b) return true;
			else if(a[end] == b) return true;
			else return false;
		}
		else
		{
			int temp = (end + first) / 2;
			if(a[temp] == b) return true;
			else if(a[temp] < b) return SeparateSearch(a, b, temp, end);
			else return SeparateSearch(a, b, first, temp);
		}
	}

	public static int GCD(int x, int y)
	{
		int z = Math.max(x, y) % Math.min(x, y);
		if(z == 0) return Math.min(x, y);
		return GCD(z, Math.min(y, x));
	}

	public static int SelectionSort(int a[])
	{
		int Select = 0;
		for(int j = 0; j < a.length - 1; j++)
		{
			int[] min = {0, Integer.MAX_VALUE};
			for(int i = j; i < a.length; i++)
			{
				if(min[1] > a[i])
				{
					min[1] = a[i];
					min[0] = i;
				}
			}
			if(j != min[0])
			{
				Select++;
				swap(a, min[0], j);
			}
		}
		return Select;
	}

	public static int BubbleSort(int a[])
	{
		int swapp = 0;
		boolean flag = true;
		while(flag)
		{
			flag = false;
			for(int i = 0; i < a.length - 1; i++)
			{
				if(a[i] > a[i+1])
				{
					swapp++;
					swap(a, i, i+1);
					flag = true;
				}
			}
		}
		return swapp;
	}

	public static void swap(int[] a, int x, int y)
	{
		a[x] = a[x] ^ a[y];
		a[y] = a[x] ^ a[y];
		a[x] = a[x] ^ a[y];
	}

	public static String[] inputOne() throws IOException
	{
		String str2 = br.readLine();
		String[] str = new String[str2.length()];
		for(int i = 0; i < str.length; i++)
		{
			if(i < str.length - 1)
			{
				str[i] = str2.substring(i, i+1);
			}
			else
			{
				str[i] = str2.substring(i);
			}
		}
		return str;
	}

	public static String[] input(int Num) throws IOException
	{
		String str[] = new String[Num];
		String str2 = br.readLine();
		int j = 0;
		for(int i = 0; i < Num; i++)
		{
			if(i < Num - 1)
			{
				str[i] = str2.substring(j, str2.indexOf(" ", j));
				j = str2.indexOf(" ", j) + 1;
			}
			else
			{
				str[i] = str2.substring(j);
			}
		}
		return str;
	}
	//*/

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	 */




}



Measured memory_bytes: 132580