N,K=map(int,input().split())
S=input()

SUM=[0]
for s in S:
    if s=="(":
        SUM.append(SUM[-1]+1)
    else:
        SUM.append(SUM[-1]-1)

if S[K-1]=="(":
    for i in range(K+1,N+1):
        if SUM[i]==SUM[K]-1:
            print(i)
            break
else:
    for i in range(K-1,-1,-1):
        if SUM[i]==SUM[K]:
            print(i+1)
            break