long long bs(long long x,long long y)
{
    printf("L = %lld, R = %lld\n",x,y);
    if (x==y) return x;
    long long mid=(x+y)/2;
    if (check(mid)) return bs(x,mid);
    return bs(mid+1,y);
}
int main()
{
    bs(-100,100);
}