#include <iostream>
using namespace std;

int buy_ice_box(int n, int *box){
    int cost = 0;
    int free = 0;
    for (int i = 0; i < n; i++){
        int ice = box[i];
        if (free > 0){
            free -= 1;
        } else {
            cost += 1;
        }
        if (ice == 2){
            free += 2;
        } else if (ice == 1){
            free += 1;
        }
    }
    return cost;
}

int buy_ice(int k, int *box){
    int cost = 0;
    int free = 0;
    for (int i = 0; i < k; i++){
        int ice = box[i];
        if (free > 0){
            free -= 1;
        } else {
            cost += 1;
        }
        if (ice == 2){
            free += 2;
        } else if (ice == 1){
            free += 1;
        } 
    }
    return cost;
}

int main(){
    int n, k;
    cin >> n >> k;
    int box[n];
    int cost_sum = 0;
    int cost_box = buy_ice_box(n, box);
    cost_sum += (k / n) * cost_box;
    cost_sum += buy_ice(k % n, box);
    cout << cost_sum << endl;
    
    return 0;
}