// https://oj.uz/problem/view/IOI17_prize
#include "prize.h"
#include<array>
// simple wrapper over ask
std::array<int,2> sk(int x){
auto v=ask(x);
return {{v[0],v[1]}};
}
int maxsk;
int f(int l,std::array<int,2> lp,int r,std::array<int,2> rp){
// return -1 if not found inside ]l..r[ , else index
while(l+1<r&&lp[0]+lp[1]<maxsk){ // there are at most ~500 such element (non-lollipop) in total
++l;
lp=sk(l);
if(lp[0]+lp[1]==0)return l;
}
while(r-1>l&&rp[0]+rp[1]<maxsk){
--r;
rp=sk(r);
if(rp[0]+rp[1]==0)return r;
}
if(l+1==r)return -1;
if(lp==rp)return -1; // [l] == [r], and no number > l or r in range
int mid=(l+r)/2;
auto mp=sk(mid);
if(mp[0]+mp[1]==0)return mid;
int res=f(l,lp,mid,mp);
if(res>=0)return res;
return f(mid,mp,r,rp);
}
int find_best(int n) {
maxsk=0;
std::array<std::array<int,2>,500> z;
for(int i=std::min(500,n);i--;){
z[i]=sk(i);
maxsk=std::max(maxsk,z[i][0]+z[i][1]);
}
return f(-1,{0,n},n,{n,0});
}
