import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken.to!int; } long readLong() { return readToken.to!long; } real readReal() { return readToken.to!real; } bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } } bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } } int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; } int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); } int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); } int N; int Ask(int k) { if (k == 0) return 0; if (k == N) return N / 2; writefln("? %s", k); stdout.flush; const s = readInt; if (s == -1) { import core.stdc.stdlib; exit(0); } return s; } void Answer(int l, int r) { writefln("! %s %s", l + 1, r); stdout.flush; } int calc(int l, int r) { const res = Ask(r) - Ask(l); return (r - l) - 2 * res; } void main() { N = readInt; const half = calc(0, N / 2); if (half == 0) { Answer(0, N / 2); return; } int lo = 0, hi = N; for (; lo + 1 < hi; ) { const mid = (lo + hi) / 2; const l = mid / 2, r = N / 2 + (mid + 1) / 2; const res = calc(l, r); debug { writeln(l, " ", r, ": ", res); } if (res == 0) { Answer(l, r); return; } (((half < 0) == (res < 0)) ? lo : hi) = mid; } assert(false); }