#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC oprimize("unrol-loops")

#define vec vector
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define int long long

using namespace std;

typedef pair<int, int> pii;

const int inf = 2e18;
int mod = 100000007;


void solve(){
    int n;
    cin>>n;
    string s;
    cin>>s;
    vec<int> a;
    for(int i = 0;i<n;i++){
        if(i+1 < s.size() && s[i] == '(' && s[i+1] == ')'){
            a.push_back(-1);
            a.push_back(0);
            a.push_back(-2);
            i++;
        }
        else{
            if(s[i] == '('){
                a.push_back(-1);
            }
            else{
                a.push_back(-2);
            }
        }
    }

    while(a.size() > 1){
        vec<int> b;
        for(int i = 0;i<a.size();i++){
            if(a[i] == -1){
                if(i+1 < a.size() && a[i+1] >=0 && i+2 < a.size() && a[i+2] == -2){
                    b.push_back(a[i+1] + 1);
                    i+=2;
                }
                else{
                    b.push_back(-1);
                }
            }
            else{
                if(a[i] >= 0){
                    if(i+1 < a.size() && a[i+1] >= 0){
                        b.push_back(a[i] * a[i+1]);
                        i++;
                    }
                    else{
                        b.push_back(a[i]);
                    }
                }
                else{
                    b.push_back(-2);
                }
            }
        }
        a = b;
    }
    cout << a[0] << "\n";

}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int tests = 1;
    while(tests--){
        solve();
    }
}