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#include <cstdio>
#include <utility>
#include <vector>
#include <list>
#include <algorithm>

const int mod = 1000000007;


typedef struct node {
    node* l_son;
    node* r_son;
    int value = -1;
} Node;

typedef struct path_el {
    int num;
    bool positive;
} Path_el;

typedef std::list<Path_el> Path;

Node* nope = new Node;
Node* one = new Node;

Node* trees[1000001];

int n;

std::vector < std::pair<int, Path> > paths;



bool compare(const Path_el& e1, const Path_el& e2) {
    return e1.num < e2.num;
}

bool compare_paths(const  std::pair<int, Path>& e1, const  std::pair<int, Path>& e2) {
    return e1.first < e2.first;
}

void read_clause() {
    char c;
    bool positive;
    int val;
    Path path;
    Path_el elt;
    bool end = false;

    while (!end && scanf("%c", &c)) {
        switch (c) {
        case 'x':
            positive = true;
            scanf("%d", &val);
            elt.positive = positive;
            elt.num = val;
            path.push_back(elt);
            break;
        case '~':
            positive = false;
            scanf("%c", &c);
            scanf("%d", &val);
            elt.positive = positive;
            elt.num = val;
            path.push_back(elt);
            break;
        case ')':
            end = true;
        }
    }

    path.sort(compare);
    paths.push_back(std::make_pair(path.front().num, path));
}

void load_data() {
    scanf("%d", &n);
    char c;

    while (scanf("%c", &c) != -1) {
        switch (c) {
        case '(': read_clause();
        }
    }

    std::sort(paths.begin(), paths.end(), compare_paths);
}

void init_trees() {
    nope->value = 0;
    one->value = 1;

    trees[n] = new node;

    trees[n]->l_son = one;
    trees[n]->r_son = one;

    for (int i = n - 1; i >= 1; i--) {
        trees[i] = new node;

        trees[i]->l_son = trees[i + 1];
        trees[i]->r_son = trees[i + 1];
    }
}

void insert_path_elt(std::list<path_el>& list, Node* node) {
    while (true) {
        auto elt = list.front();
        list.pop_front();

        if (list.empty()) {
            if (elt.positive) {
                node->l_son = nope;
            }
            else {
                node->r_son = nope;
            }
            return;
        }

        Node* l = node->l_son;
        Node* r = node->r_son;

        Node* changed;
        Node* new_changed = new Node;

        if (elt.positive && l->value != 0) {
            changed = l;
            node->l_son = new_changed;
        }
        else if (elt.positive) {
            return;
        }
        else if (r->value != 0) {
            changed = r;
            node->r_son = new_changed;
        }
        else {
            return;
        }

        new_changed->l_son = changed->l_son;
        new_changed->r_son = changed->r_son;

        node = new_changed;
    }

}

void insert_path() {
    auto path_p = paths.back();
    paths.pop_back();
    auto path = path_p.second;
    int insert_tree = path_p.first;

    insert_path_elt(path, trees[insert_tree]);
}

int sum_tree(Node* node) {
    if (node->value == -1) {
        int sum = sum_tree(node->r_son) + sum_tree(node->l_son);
        sum %= mod;
        node->value = sum;
    }

    return node->value;
}

int main(void) {
    auto& tre = trees;
    auto& pat = paths;
    load_data();
    init_trees();
    while (!paths.empty()) {
        insert_path();
    }

    for (int i = n; i >= 1; i--) {
        sum_tree(trees[i]);
    }

    printf("%d\n", sum_tree(trees[1]));

    return 0;
}