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// tested by Hightail: https://github.com/dj3500/hightail
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define INF 1001001001
#define FOR(i,n) for(int (i)=0;(i)<(n);++(i))
#define FORI(i,n) for(int (i)=1;(i)<=(n);++(i))
#define mp make_pair
#define pii pair<int,int>
#define ll long long
#define vi vector<int>
#define SZ(x) ((int)((x).size()))
#define fi first
#define se second
#define wez(n) int (n); scanf("%d",&(n));
#define wez2(n,m) int (n),(m); scanf("%d %d",&(n),&(m));
#define wez3(n,m,k) int (n),(m),(k); scanf("%d %d %d",&(n),&(m),&(k));
inline void pisz(int n) { printf("%d\n",n); }
template<typename T,typename TT> ostream& operator<<(ostream &s,pair<T,TT> t) {return s<<"("<<t.first<<","<<t.second<<")";}
template<typename T> ostream& operator<<(ostream &s,vector<T> t){FOR(i,SZ(t))s<<t[i]<<" ";return s; }
#define DBG(vari) cout<<"["<<__LINE__<<"] "<<#vari<<" = "<<(vari)<<endl;
#define ALL(t) t.begin(),t.end()
#define FOREACH(i,t) for (__typeof(t.begin()) i=t.begin(); i!=t.end(); i++)
#define TESTS wez(testow)while(testow--)
#define REP(i,a,b) for(int (i)=(a);(i)<=(b);++i)
#define REPD(i,a,b) for(int (i)=(a); (i)>=(b);--i)
#define REMAX(a,b) (a)=max((a),(b));
#define REMIN(a,b) (a)=min((a),(b));
#define IOS ios_base::sync_with_stdio(0);

template <typename T, typename R>
void wywal (vector<R> &v, const T &lambda) {
   v.erase(remove_if(ALL(v), lambda), v.end());
}

struct Dis {
   vector<bool> v;
   int A, B;
   int id;
};
ostream& operator<<(ostream &s, const Dis &d) {
   s << '[' << d.A << ',' << d.B << ',';
   for (bool b : d.v) {
      s << b;
   }
   s << ']';
   return s;
}
bool comp (const Dis &d1, const Dis &d2) {
   return mp(d1.B - d1.A, d1.id) < mp(d2.B - d2.A, d2.id);
}
bool comp2 (const Dis &d1, const Dis &d2) {
   return mp(mp(d1.A, d1.B), d1.id) < mp(mp(d2.A, d2.B), d2.id);
}

pair<int,bool> czytajZm (const string &t) {
   int pos = 1;
   if (t[0] == '~') ++pos;
   return mp(atoi(t.substr(pos).c_str()), t[0] != '~');
}

Dis czytajDis (const string &t) {
   vi wedge;
   FOR(i,SZ(t)) if (t[i] == 'v') wedge.pb(i);
   vector<pair<int,bool>> vars;
   if (wedge.empty()) {
      vars.pb(czytajZm(t));
   } else {
      vars.pb(czytajZm(t.substr(0,wedge[0]-1)));
      FOR(u,SZ(wedge)-1) {
         vars.pb(czytajZm(t.substr(wedge[u]+2, wedge[u+1]-wedge[u]-3)));
      }
      vars.pb(czytajZm(t.substr(wedge.back()+2, SZ(t)-wedge.back()-2)));
   }
   sort(ALL(vars));
   Dis d;
   d.A = vars[0].fi;
   d.B = vars.back().fi;
   for (const pair<int,bool> &it : vars) d.v.pb(it.se);
   static int nextId = 1;
   d.id = nextId++;
   return d;
}

vector<Dis> czytaj (const string &s) {
   vector<Dis> res;
   vi xory;
   FOR(i,SZ(s)) if (s[i] == '^') xory.pb(i);
   //vector<pii> roz;
   if (xory.empty()) {
      res.pb(czytajDis(s.substr(1,SZ(s)-2)));
      //roz = {{1,SZ(s)-1}};
   } else {
      res.pb(czytajDis(s.substr(1,xory[0]-3)));
      //roz = {{1,xory[0]-2}};
      FOR(u,SZ(xory)-1) {
         res.pb(czytajDis(s.substr(xory[u]+3, xory[u+1]-xory[u]-5)));
         //roz.pb({xory[u]+3, xory[u+1]-2});
      }
      res.pb(czytajDis(s.substr(xory.back()+3, SZ(s)-xory.back()-4)));
      //roz.pb({xory.back()+3, SZ(s)-1});
   }
   return res;
}

const int mod = 1000000007;
ll _val;

struct Node {
   Node* x[2];
   bool endsHere;
   ll aug = 0;
   Node () { FOR(i,2) x[i] = 0; endsHere = false; aug = 0; }
   
   bool czyJuzJest (const vector<bool> &v, int pos) {
      if (endsHere) return true;
      if (pos == -1) return false;
      if (0 == x[v[pos]]) return false;
      return x[v[pos]]->czyJuzJest(v,pos-1);
   }
   
   ll findAug (const vector<bool> &v, int pos) {
      if (pos == -1) return aug;
      if (0 == x[v[pos]]) return false;
      return x[v[pos]]->findAug(v, pos-1);
   }
   
   void dodaj (const vector<bool> &v, int pos) {
      if (pos == -1) {
         endsHere = 1;
         return;
      }
      if (0 == x[v[pos]]) {
         x[v[pos]] = new Node();
      }
      x[v[pos]]->dodaj(v, pos-1);
   }
   
   void dodajval (const vector<bool> &v, int pos) {
      aug += _val;
      if (aug > mod) aug -= mod;
      if (pos == -1) {
         return;
      }
      if (0 == x[v[pos]]) {
         assert(0);
         x[v[pos]] = new Node();
      }
      x[v[pos]]->dodajval(v, pos-1);
   }
};

const int N = 1000007;
Node root[N];

bool juzJest (const Dis &d) {
   // jesli na swojej drodze spotkam cos istniejacego, to fail
   REPD(x,d.B,d.A) {
      if (root[x].czyJuzJest(d.v, x - d.A)) return true;
   }
   return false;
   //return root[d.B].czyJuzJest(d.v, SZ(d.v)-1);
}

void dodaj (const Dis &d) {
   root[d.B].dodaj(d.v, SZ(d.v) - 1);
}

ll compatible (const Dis &d) {
   ll res = 0;
   REPD(x,d.B,d.A) {
      res += root[x].findAug(d.v, x - d.A);
   }
   return res % mod;
}

ll res[N];
ll pow2[N], powinv2[N];
const ll inv2 = 500000004;

vi endingAt[N];

int main () {
   pow2[0] = 1;
   REP(x,1,1000000) pow2[x] = pow2[x-1] * 2 % mod;
   powinv2[0] = 1;
   REP(x,1,1000000) powinv2[x] = powinv2[x-1] * inv2 % mod;
   
   IOS
   int n;
   cin >> n;
   string linia;
   getline(cin, linia);
   getline(cin, linia);
   vector<Dis> D = czytaj(linia);
   //DBG(D);
   sort(ALL(D), comp);
   wywal(D, [] (const Dis &d) {
      if (juzJest(d)) {
         return 1;
      } else {
         dodaj(d);
         return 0;
      }
   });
      
   //DBG(D);
   sort(ALL(D), comp2);
   
   FOR(j,SZ(D)) {
      endingAt[D[j].B].pb(j);
   }
   
   int nextEndToCheck = 0;
   ll sumOfResForAlreadyEnded = 0;
   FOR(j,SZ(D)) {
      while (nextEndToCheck < D[j].A) {
         for (int i : endingAt[nextEndToCheck]) {
            sumOfResForAlreadyEnded += res[i];
         }
         ++nextEndToCheck;
         sumOfResForAlreadyEnded %= mod;
      }
      
      res[j] = pow2[n - (D[j].B - D[j].A + 1)];
      res[j] -= powinv2[D[j].B - D[j].A + 1] * sumOfResForAlreadyEnded % mod;
      res[j] -= compatible(D[j]) * powinv2[D[j].B] % mod;
      res[j] %= mod;
      
      // wrzuc to do trie
      _val = res[j] * pow2[D[j].B] % mod;
      if (_val < 0) _val += mod;
      root[D[j].B].dodajval(D[j].v, SZ(D[j].v) - 1);
   }
   
   // wynik
   ll sumres = 0;
   FOR(j,SZ(D)) sumres += res[j];
   
   sumres = pow2[n] - sumres;
   
   sumres %= mod;
   if (sumres < 0) sumres += mod;
   cout << sumres;
}