#include<bits/stdc++.h>
main(){int n,k,a=0;std::string s;std::cin>>n>>k>>s;k--;if(s[k]=='(')do{if(s[k]=='(')a++;else a--;}while(a&&k++);else do{if(s[k]=='(')a++;else a--;}while(a&&k--);printf("%d\n",++k);}