#include <bits/stdc++.h> using namespace std; typedef signed long long ll; #define _P(...) (void)printf(__VA_ARGS__) #define FOR(x,to) for(x=0;x<(to);x++) #define FORR(x,arr) for(auto& x:arr) #define FORR2(x,y,arr) for(auto& [x,y]:arr) #define ALL(a) (a.begin()),(a.end()) #define ZERO(a) memset(a,0,sizeof(a)) #define MINUS(a) memset(a,0xff,sizeof(a)) template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;} template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;} //------------------------------------------------------- int N; string S; int dp[202020]; vector<int> A; void solve() { int i,j,k,l,r,x,y; string s; cin>>N>>S; int cur=0; string T=S; A={0}; FOR(i,N) { if(S[i]=='?') { if(cur||i!=A.back()) { T[i]=')'; } else { if(i==N-1||S[i+1]!='(') { T[i]='('; } else { T[i]=')'; } } } if(T[i]=='(') { cur++; } else if(T[i]==')') { cur--; if(cur<0) { cur=0; if(i!=A.back()) A.push_back(i+1); } } } T=S; int ret=A.size()-1+(A.back()!=N); int num=0,prev=N; cur=0; T=S; for(i=N-1;i>=0;i--) { if(S[i]=='?') { if(cur||prev!=i+1) { T[i]='('; } else { if(i==0||S[i-1]!=')') { T[i]=')'; } else { T[i]='('; } } } if(T[i]==')') { cur++; } else if(T[i]=='(') { cur--; if(cur<0) { cur=0; if(i+1!=prev) num++; prev=i; x=lower_bound(ALL(A),i)-A.begin()-1; ret=max(ret,num+x+(A[x]-1!=i)); } } } cout<<ret<<endl; } int main(int argc,char** argv){ string s;int i; if(argc==1) ios::sync_with_stdio(false), cin.tie(0); FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin); cout.tie(0); solve(); return 0; }