#include "souvenirs.h"
#include <bits/stdc++.h>
#include <utility>
#include <vector>
using namespace std;
pair <vector<int>, long long> transaction(long long M);
void buy_souvenirs(int N, long long P0) {
pair <vector<int>, long long> res;
if ( N == 2 ) {
transaction ( P0 - 1 );
} else if ( N == 3 ) {
res = transaction ( P0 - 1 );
if ( res.first.size() == 1 ) {
transaction ( P0 - 1 - res.second - 1 );
transaction ( P0 - 1 - res.second - 1 );
} else {
transaction ( ( P0 - 1 - res.second ) / 2 );
}
} else if ( P0 == N ) {
for ( int i = 1; i < N; i++ ) {
for ( int j = 0; j < i; j++ ) {
transaction ( N - i );
}
}
} else {
pair <long long, long long> a[N];
for ( int i = 0; i < N; i++ ) {a[i].first = 0; a[i].second = 0;}
a[0] = { P0, 1 };
for ( int i = 1; i < N; i++ ) {
res = transaction( a[i - 1].first - 2 );
if ( i == N - 1 ) {
while ( a[i].second < i ) {
a[i].second++;
transaction( a[i - 1].first - 1 );
}
} else if ( res.first[0] == i ) {
a[i].first = a[i - 1].first - 2;
a[i].second++;
while ( a[i].second < i ) {
a[i].second++;
transaction( a[i - 1].second - 2 );
}
} else {
a[i].first = a[i - 1].first;
a[i + 1].second++;
while ( a[i].second < i ) {
a[i].second++;
transaction( a[i - 1].second - 1 );
}
}
}
}
return;
}
