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#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

#define MAX_N 1000000
#define MOD 1000000007

int n;
string str;
vector<vector<pair<int, bool>>> data;

int ret = 0;
int D[MAX_N];

void f(int i){
    if(i < n){
        D[i] = 0;
        f(i + 1);
        D[i] = 1;
        f(i + 1);
    }else{
        bool all = 1;
        for(auto& v : data){
            bool any = 0;
            for(auto& p : v){
                if(p.second ^ D[p.first]){
                    any = 1;
                    break;
                }
            }
            if(!any){
                all = 0;
                break;
            }
        }
        if(all){
            if(++ret >= MOD)ret -= MOD;
        }
    }
}

int main(){
    ios::sync_with_stdio(0);

    cin>>n;
    getline(cin, str);
    getline(cin, str);
    int value = 0;
    bool neg = 0;
    for(int a=0; a<int(str.size()); ++a){
        if(str[a] >= '0' && str[a] <= '9'){
            value = value * 10 + (str[a] - '0');
        }else{
            if(value != 0)data.back().push_back({value - 1, neg});

            if(str[a] != 'x'){
                value = 0;
                neg = 0;
            }

            if(str[a] == '('){
                data.push_back({});
            }else if(str[a] == '~'){
                neg = 1;
            }
        }
    }

    f(0);
    cout<<ret;

    return 0;
}