Submission #2916668

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Source Code Expand

#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <utility>
#include <queue>
#include <set>
#include <map>
#include <deque>
#include <iomanip>
#include <cstdio>

using namespace std;
typedef  long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define  MP make_pair
#define  PB push_back
#define inf  1000000007
#define rep(i,n) for(int i=0;i<(int)(n);++i)

int main(){
    int c;
    ll n,k;
    cin >> c;
    rep(zz,c){
        cin >> n >> k;
        ll cnt = 0;
        cnt = (n-1)/2+1;
        if(cnt<k){
            cout << -1 << endl;
            continue;
        }
        if(n%2==0)n--;
        ll q = n*2/3;
        ll p = (n+1)/2;
        ll a,b,ans;
        a = q/4-(p-1)/4;
        b = n/2-q/2;
        ans = 0;
        if(k<=a){
            ans = (p+1)/2+2*(k-1);
        }else if(k<=a+b){
            ans = (q+2)/2+k-a-1;
        }else if(k<=b+q-p+1){
            k-=a+b;
            ll z = (k+2)/3;
            k -= (z-1)*3;
            ans = p+4*(z-1);
            for(int i=0;i<4;i++){
                if(ans%4!=0){
                    k--;
                    if(k==0)break;
                }
                ans++;
            }
        }else{
            if(q%2==0){
                ans = q+1;
            }else{
                ans = q+2;
            }
            k -= (b+q-p+1)+1;
            ans += 2*k;
        }
        cout << ans << endl;
    }
    return 0;
}

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