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#include <bits/stdc++.h>
using namespace std;
const int MXN=100;
int dp[MXN][MXN];
int solve(int p, int k, string &s)
{
	if (p>k)
	{
		dp[p][k]=0;
		return 0;
	}
	if (dp[p][k]!=-1) return dp[p][k];
	solve(p+1, k, s);
	solve(p, k-1, s);
	solve(p+1, k-1, s);
	dp[p][k]=dp[p+1][k]+dp[p][k-1]-dp[p+1][k-1];
	int cnt=0, mn=0;
	for (int i=p; i<=k; i++)
	{
		cnt+=(s[i]=='('? 1 : -1);
		mn=min(mn, cnt);
	}
	dp[p][k]+=(cnt==0 && mn==0);
	return dp[p][k];
}
int main()
{
	memset(dp, -1, sizeof(dp));
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int n, k; cin>>n>>k;
	string w; cin>>w;
	//~ while (true)
	//~ {
		//~ int x, y; cin>>x>>y;
		//~ cout<<solve(x, y, w)<<endl;
	//~ }
	int ans=INT_MAX;
	for (int i=1; i<(1<<(n-1)); i++)
	{
		if (__builtin_popcount(i)!=k-1) continue;
		int pre=0, pom=0;
		for (int j=0; j<n; j++)
		{
			if (i&(1<<j))
			{
				pom+=solve(pre, j, w);
				pre=j+1;
			}
		}
		pom+=solve(pre, n-1, w);
		ans=min(ans, pom);
	}
	cout<<ans<<"\n";
}