#include <bits/stdc++.h>
using namespace std;
using i32 = int;
using i64 = long long;
template <typename T>
using V = vector<T>;
template <typename T>
using VV = V<V<T>>;
template <typename T>
using VVV = V<VV<T>>;
template <typename T>
bool chmin(T &x, const T &y) {
if (x > y) {
x = y;
return true;
}
return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
if (x < y) {
x = y;
return true;
}
return false;
}
#define OVERRIDE4(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, l, r) for (i32 i = (i32)(l); i < (i32)(r); ++i)
#define REP(...) OVERRIDE4(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER2(i, n) for (i32 i = (i32)(n)-1; i >= 0; --i)
#define PER3(i, l, r) for (i32 i = (i32)(r)-1; i >= (i32)(l); --i)
#define PER(...) OVERRIDE4(__VA_ARGS__, PER3, PER2)(__VA_ARGS__)
#define LEN(x) (i32) size(x)
#define ALL(x) begin(x), end(x)
void dbg(i32 x) { cerr << x; }
void dbg(i64 x) { cerr << x; }
template <typename T, typename U>
void dbg(pair<T, U> p) {
cerr << "(";
dbg(p.first);
cerr << ", ";
dbg(p.second);
cerr << ")";
}
template <typename T>
void dbg(V<T> arr) {
cerr << "[";
REP(i, LEN(arr)) {
if (i) {
cerr << ", ";
}
dbg(arr[i]);
}
cerr << "]";
}
void debug() { cerr << '\n'; }
template <typename Head, typename... Tail>
void debug(Head head, Tail... tail) {
dbg(head);
cerr << ", ";
debug(tail...);
}
#ifdef DEBUGF
#define DBG(...) \
do { \
cerr << #__VA_ARGS__ << " : "; \
debug(__VA_ARGS__); \
} while (false)
#else
#define DBG(...) (void)0
#endif
#include "prize.h"
pair<i32, i32> ask2(i32 x) {
static i32 q;
++q;
if (q == 10000) {
assert(false);
}
V<i32> ret = ask(x);
return pair<i32, i32>(ret[0], ret[1]);
}
i32 subtask_1(i32 n) {
i32 ok = -1, ng = n - 1;
while (ng - ok > 1) {
i32 mid = (ok + ng) / 2;
auto [l, r] = ask2(mid);
if (r) {
ok = mid;
} else {
ng = mid;
}
}
return ng;
}
i32 find_best(i32 n) {
mt19937 mt(random_device{}());
i32 cands = 0;
{
uniform_int_distribution<> dist(0, n - 1);
REP(i, 50) {
auto [l, r] = ask2(dist(mt));
chmax(cands, l + r);
}
}
auto rec = [&](auto rec, i32 l, i32 r, i32 lc, i32 rc) -> i32 {
i32 tc = cands - lc - rc;
if (tc == 0) {
return -1;
}
DBG(l, r, lc, rc);
i32 mid = (l + r) / 2;
if (r - l > 10) {
uniform_int_distribution<> dist(l, r - 1);
mid = dist(mt);
}
auto [lm, rm] = ask2(mid);
DBG(mid, lm, rm);
if (lm + rm == 0) {
return mid;
}
if (lm + rm == cands) {
i32 tmp = rec(rec, l, mid, lc, rm);
if (tmp != -1) {
return tmp;
}
return rec(rec, mid, r, lm, rc);
}
// to left
if (lm != 0) {
i32 x = mid - 1;
while (x >= l) {
auto [lx, rx] = ask2(x);
if (lx + rx == 0) {
return x;
}
if (lx + rx == cands) {
i32 tmp = rec(rec, l, x, lc, rx);
if (tmp != -1) {
return tmp;
}
break;
}
if (lm == 0) {
break;
}
--x;
}
}
// to right
{
i32 x = mid + 1;
while (x < r) {
auto [lx, rx] = ask2(x);
if (lx + rx == 0) {
return x;
}
if (lx + rx == cands) {
i32 tmp = rec(rec, x + 1, r, lx, rc);
if (tmp != -1) {
return tmp;
}
break;
}
++x;
}
}
return -1;
};
i32 ans = rec(rec, 0, n, 0, 0);
return ans;
}
