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 $0$.