#include "coins.h"
#include <bits/stdc++.h>
using namespace std; using ii = pair<int,int>; using ll = long long; using vi = vector<int>;
#define rep(i,a,b) for (auto i = (a); i <= (b); ++i)
#define per(i,a,b) for (auto i = (b); i >= (a); --i)
#define all(x) begin(x), end(x)
#define siz(x) int((x).size())
#define Mup(x,y) x = max(x,y)
#define mup(x,y) x = min(x,y)
#define fi first
#define se second
#define dbg(...) fprintf(stderr,__VA_ARGS__)
vi coin_flips(vi b, int c) {
int sum=0;
rep(i,0,63) sum ^= b[i]*i;
rep(i,0,63) if ((sum^i) == c) return {i};
assert(0);
}
int find_coin(vi b) {
int sum=0;
rep(i,0,63) sum ^= b[i]*i;
return sum;
}
