import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.NoSuchElementException;

public class Main {
    static FastScanner scan = new FastScanner();
    static PrintWriter out = new PrintWriter(System.out);

    public static void main(String[] args) {
        int res = ask(100);
        if(res == 0) {
            System.out.println("! 100");
            return;
            
        } else if(res < 0) {
            for(int i=2; i<=100; i++) {
                res = ask(0);
                if(res == 0) {
                    System.out.println("! " + (i-1));
                    return;
                }
            }
        }
        
        int l = 100;
        int r = 1000000000;
        int m = 0;
        int count = 1;
        while(l < r) {
            m = (l+r)/2;
            res = ask(m-count);
            count++;
            
            if(res == 0) {
                System.out.println("! " + m);
                return;
            } else if(res > 0) {
                l = m+1;
            } else {
                r = m;
            }
        }
        
        System.out.println("! " + l);
    }

    static int ask(int y) {
        out.println("? " + y);
        out.flush();
        int res = scan.nextInt();
        return res;
    }
    
    static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        private void skipUnprintable() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
        }

        public boolean hasNext() {
            skipUnprintable();
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public int nextInt() {
            return (int) nextLong();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }
    }
}