#include <iostream>

using namespace std;

int main()
{
        int n, k;
        int i;
        int show, type;
        int showTotal = 0, typeTotal = 0;
        int neededType;

        cin >> n >> k;
        for ( i = 1; i <= n; i++)
        {
                cin >> show >> type;

                if (show - type == 2)
                        showTotal = typeTotal = 0;
                else
                {
                        showTotal += show;
                        typeTotal += type + 2;
                }
        }
        neededType = k + showTotal - typeTotal - 2;
        if (neededType > 0 && neededType < 101)
                cout << neededType << endl;
        else
        {
                cout << "Big Bang!" << endl;
        }
        return 0;
}