import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Iterator;


public class Main_yukicoder253 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        int count = 1;
        if (ask(sc, pr, 40) < 0) {
        	while (ask(sc, pr, 9) > 0) {
        		count++;
        	}
        	
        	pr.printf("! %d\n", 9 + count);
        } else {
        	int l = 39;
        	int r = 1000000001;
    		while (r > l) {
    			int mid = (r + l) / 2;
    			count++;
    			if (ask(sc, pr, mid) <= 0) {
    				r = mid;
    			} else {
    				l = mid + 1;
    			}
    		}

    		int tmp = r - count;
        	while (ask(sc, pr, tmp) > 0) {
        		count++;
        	}
        	
        	pr.printf("! %d\n", tmp + count);
        }

        pr.close();
        sc.close();
    }

	private static int ask(Scanner sc, Printer pr, int i) {
		pr.printf("? %d\n", i);
		pr.flush();
		return sc.nextInt();
	}

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;
		
		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}
		
		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}
		
		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}