SRM639

AliceGameEasy.cpp

class AliceGameEasy {
    public:
    long long findMinimumValue(long long x, long long y) {
      long long ans = 0;
      long long sum = x+y,r=0,l=3037000490;
      long long i=(r+l);
      while(true)
	{
	  i=(r+l)/2;
	  if((i*(i+1))/2 == sum)
	    break;
	  else if((i*(i+1))/2 > sum)
	      l=((r+l)/2)-1;
	  else if((i*(i+1))/2 < sum)
	      r=((r+l)/2)+1;
	    if(r>l)
	      return -1;
	}
      while(x>0)
	{
	  if(x>=i)
	    {
	      ans++;
	      x-=i;
	      i--;
	    }
	  else
	    {
	      i=x;
	    }
	}
      return ans;
    }
};