n,k=map(int,input().split())
s=input()
count=0
if s[k-1]=="(":
    for i in range(k,n):
        if s[i]=="(":
            count+=1
        elif s[i]==")":
            count-=1
            if count==-1:
                print(i+1)
                break

elif s[k-1]==")":
    s=s[::-1]
    for i in range(n-k+1,n):
        if s[i]==")":
            count+=1
        elif s[i]=="(":
            count-=1
            if count==-1:
                print(n-i)
                break