Bob is biking on a trail with ~N~ sections. This trail has uphills, downhills, and flat sections, denoted by U, D, and F, respectively. He starts with a speed of ~K~, and will bike through the entire trail. When biking:

• On uphill sections, Bob will lose ~1~ unit of speed.
• On downhill sections, Bob will gain ~1~ unit of speed.
• On flat sections, Bob's speed will not change.

If Bob's speed becomes ~0~, he will have to get off his bike and walk until he reaches either a downhill section or the end of the trail. His speed cannot be negative.

How many total sections will Bob have to walk on?

Constraints

~1 \le N, K \le 10^4~

Input Specification

The first line will contain two space-separated integers ~N~ and ~K~.

The second and final line will contain a string of length ~N~ with only the characters U, D, and F.

Output Specification

Output one integer on one line, the number of sections Bob will have to walk on.

Sample Input

11 1
FUDDDUDUUUF

Sample Output

3

Explanation

Bob has to walk the second section and from the tenth section to the end of the trail, as in these sections, his speed is ~0~.