#include<bits/stdc++.h> using namespace std; pair<vector<int>,long long> transaction(long long M); int cnt=0; void buy_souvenirs(int N,long long p0) { auto [v,r]=transaction(p0-1); if(v.size()==1) { transaction(p0-r-2); transaction(p0-r-2); } else { long long s=p0-1-r; transaction(s/2); } }