#include "prize.h"
#include <iostream>
using namespace std;
int sub1(int st, int ed) {
int mid = (st + ed) / 2;
vector<int> v = ask(mid);
int l = v[0], r = v[1];
if(l == 1) return sub1(st, mid-1);
else if(r == 1) return sub1(mid+1, ed);
else return mid;
}
int ls[200100], rs[200100], maxLR;
// u = sum of cheapest V's left and right
bool isDiamond(int i);
void makeLR(int i);
int findDiamond(int st, int ed);
int sub2(int n) { // idx: 0 ~ n-1
for(int i=0; i<n; i++) {
ls[i] = -1; rs[i] = -1;
}
makeLR(0);
if(isDiamond(0)) return 0;
makeLR(n-1);
if(isDiamond(n-1)) return n-1;
return findDiamond(0, n-1);
}
bool isDiamond(int i) {
return ls[i] + rs[i] == 0;
}
void makeLR(int i) {
if(ls[i] != -1 && rs[i] != -1) return;
vector<int> v = ask(i);
ls[i] = v[0]; rs[i] = v[1];
}
int findDiamond(int st, int ed) {
if(ed - st <= 1) return -1;
// else
if(ls[st] + rs[st] == ls[ed] + rs[ed]) {
// if st~ed, no prize
if(ls[ed] - ls[st] == 0) return -1;
// else
int mid = (st + ed) / 2;
makeLR(mid);
if(isDiamond(mid)) return mid;
int resL = findDiamond(st, mid); // check initial condition
int resR = findDiamond(mid, ed);
return resL > resR ? resL:resR;
}
else if(ls[st] + rs[st] < ls[ed] + rs[ed]) {
makeLR(st+1);
if(isDiamond(st+1)) return st+1;
else return findDiamond(st+1, ed);
}
else {
makeLR(ed-1);
if(isDiamond(ed-1)) return ed-1;
else return findDiamond(st, ed-1);
}
}
int find_best(int n) {
return sub2(n);
}
