N,M=map(int,input().split())
S=list(input())
L=[0]
for i in range(N):
    if S[i]=="(":
        L.append(L[-1]+1)
    else:
        L.append(L[-1]-1)
#print(L)

ans=0
if S[M-1]==")":
    for i in range(M):
        if L[i]==L[M]:
            ans=i
    print(ans+1)
else:
    for i in range(M+1,N+1):
        if L[i]==L[M]-1:
            break
    print(i)