Potassium, a genius who masters soul conversion, is observing the world line of Potas. The world line can be divided into parts and represented as an -digit decimal number (may have leading zeros) that reveals the property of time in the past and future of Potas.

For convenience, let denote the concatenation of digits , so the world line can be expressed as . When observing, Potassium focuses on the era, which consists of continuous parts in the world line. An era beginning from part to can be denoted as (), and may also have leading zeros.

When two eras are quite similar, Potassium can observe one from another by Spirit Circle. More specifically, an era can be observed from another era by Spirit Circle if and only if the following two conditions are satisfied, regardless of where and locate in originally.

1. and have the same length, i.e. ;
2. is greater than by exactly , i.e. .

Potassium is wondering: how many different pairs can be found in  that he can observe era from era . Note that two eras having the same representations but differing in the original location in are considered as different eras.

The first line contains one integer  (), denoting the number of parts in the world line of Potas.

The second line contains an -digit decimal number , denoting the representation of the world line of Potas.

Print an integer in a single line, denoting the number of different pairs  in  that Potassium can observe era  from era  by Spirit Circle.

5
10998

5

6
001100

11

In the first example, Potassium can choose  different  pairs:

1. Choose ;
2. Choose ;
3. Choose ;
4. Choose ;
5. Choose .