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#include <bits/stdc++.h>
 
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define VAR(v, i) __typeof(i) v=(i)
#define FORE(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define all(v) (v).begin(),(v).end()
 
#define PII pair<int,int>
#define mp make_pair
#define st first
#define nd second
#define pb push_back
#define lint long long int
#define VI vector<int>
 
#define debug(x) {cerr <<#x <<" = " <<x <<endl; }
#define debug2(x,y) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y <<endl; } 
#define debug3(x,y,z) {cerr <<#x <<" = " <<x << ", "<<#y<<" = "<< y << ", " << #z << " = " << z <<endl; } 
#define debugv(x) {{cerr <<#x <<" = "; FORE(itt, (x)) cerr <<*itt <<", "; cerr <<endl; }}
#define debugt(t,n) {{cerr <<#t <<" = "; FOR(it,0,(n)) cerr <<t[it] <<", "; cerr <<endl; }}
 
#define make( x) int (x); scanf("%d",&(x));
#define make2( x, y) int (x), (y); scanf("%d%d",&(x),&(y));
#define make3(x, y, z) int (x), (y), (z); scanf("%d%d%d",&(x),&(y),&(z));
#define make4(x, y, z, t) int (x), (y), (z), (t); scanf("%d%d%d%d",&(x),&(y),&(z),&(t));
#define makev(v,n) VI (v); FOR(i,0,(n)) { make(a); (v).pb(a);} 
#define IOS ios_base::sync_with_stdio(0)
#define HEAP priority_queue
 
#define read( x) scanf("%d",&(x));
#define read2( x, y) scanf("%d%d",&(x),&(y));
#define read3(x, y, z) scanf("%d%d%d",&(x),&(y),&(z));
#define read4(x, y, z, t) scanf("%d%d%d%d",&(x),&(y),&(z),&(t));
#define readv(v,n) FOR(i,0,(n)) { make(a); (v).pb(a);}
 
 
using namespace std;

const int max_n = 1e6 + 5;

int n;
vector< pair<PII, VI> > klauzule;

int znaczek[max_n];

PII zjedz_literal() {
	int sgn = 0;
	char C = getchar();
	if (C == 'x') sgn = 0;
	else {
		sgn = 1;
		C = getchar();
	}
	int licz = 0;
	C = getchar();
	while (C>='0' && C<='9') {
		licz = 10*licz + (C-'0');
		C = getchar();
	}
	return mp(licz, sgn);
}

int value[max_n];

void parse_input() {
	scanf("%d\n", &n);
	char C = getchar();
	while (1) {
		if (C == '(') {
			VI wartosci;
			PII p1 = zjedz_literal();
			int mini = p1.st, maxi = p1.st;
			value[p1.st] = p1.nd;
			C = getchar();
			while (C == 'v') {
				C = getchar();
				PII p = zjedz_literal();
				value[p.st] = p.nd;
				mini = min(mini, p.st);
				maxi = max(maxi, p.st);
				C = getchar();
			}
			FOR(j,mini, maxi+1) wartosci.pb(value[j]);
			klauzule.pb(mp(mp(mini, maxi), wartosci));
			if (C=='\n') break;
			C = getchar();
			if (C=='\n') break;
			C = getchar();
			if (C=='\n') break;
			C = getchar();
			if (C=='\n') break;
		}
	}
}

void brute_force() {
	int ans = 0;
	FOR(i,0,1<<n) {
		bool ok = true;
		FOR(j,0,klauzule.size()) {
			if (!ok) break;
			bool loc = false;
			int pocz = klauzule[j].st.st;
			FOR(k, 0, klauzule[j].nd.size()) {
				int kto = pocz + k;
				int co = klauzule[j].nd[k];
				if ((i & (1<<(kto-1)))) {
					if (co==0) loc = true;
				} else {
					if (co!=0) loc = true;
				}
			}
			if (!loc) ok = false;
		}
		if (ok) ans++;
	}
	printf("%d\n", ans);
}

int K;
int mod = 1e9 + 7;
int jd = (1+mod)/2;
int jdPW[max_n];
int minus = (mod - 1);

int soFar[max_n];
vector<int> val[max_n];
vector<PII> konce[max_n];

bool zgadza(int k1, int k2) {
	int p1 = klauzule[k1].st.st;
	int p2 = klauzule[k2].st.st;
	int kon1 = klauzule[k1].st.nd;
	int kon2 = klauzule[k2].st.nd;
	FOR(i, max(p1,p2), min(kon1, kon2) + 1) {
		if (klauzule[k1].nd[i-p1] != klauzule[k2].nd[i-p2]) return false;
	}
	return true;
}

bool zawiera(int k1, int k2) {
	int p1 = klauzule[k1].st.st;
	int p2 = klauzule[k2].st.st;
	int kon1 = klauzule[k1].st.nd;
	int kon2 = klauzule[k2].st.nd;
	if (p1 <= p2 & kon1 >= kon2) return true;
	return false;
}

void kwadraciak() {
	K = klauzule.size();
	FOR(i,0,K) {
		konce[klauzule[i].st.nd].pb(mp(-klauzule[i].st.st, i));
	}
	soFar[0] = 1;
	FOR(i,1,n+1) {
		soFar[i] = soFar[i-1];
		sort(all(konce[i]));
		FOR(j, 0, konce[i].size()) {
			int kl = konce[i][j].nd;
			/*FOR(z, klauzule[kl].st.st, klauzule[kl].st.nd+1) {
				cout <<  "x_" << z << " = " << klauzule[kl].nd[z-klauzule[kl].st.st] <<", ";
			}
			cout << endl;*/
			bool ok = true;
			FOR(l,0,j) {
				if (zgadza(kl, konce[i][l].nd)) {
					ok = false;
					break;
				}
			}
			if (!ok) {
				val[i].pb(0);
				continue;
			}
			
			int myval = 0;
			int poczateczek = klauzule[kl].st.st;
			FORD(m, i-1, poczateczek) {
				if (!ok) break;
				FOR(l, 0, konce[m].size()) {
					if (!ok) break;
					if (zgadza(kl, konce[m][l].nd)) {
						if (zawiera(kl, konce[m][l].nd)) {
							ok = false;
							if (!ok) break;
						}
						myval = (myval +  mod - ((jdPW[i-m] * 1LL * val[m][l]) % mod));
						if (myval >= mod) myval -= mod;
					}
				}
			}
			myval = (myval + mod - ((jdPW[i-poczateczek+1] * 1LL * soFar[poczateczek-1]) % mod));
			if (myval >= mod) myval -= mod;
			if (!ok) {
				val[i].pb(0);
				continue;
			}
			val[i].pb(myval);
			soFar[i] += myval;
			if (soFar[i] >= mod) soFar[i] -= mod;
		}
	}
	int ANS = soFar[n];
	FOR(i,0,n) {
		ANS = ANS + ANS;
		if (ANS >= mod) ANS -= mod;
	}
	printf("%d\n", ANS);
}



int main() {	
	parse_input();
	jdPW[0] = 1;
	jdPW[1] = jd;
	FOR(i,2,n + 1) {
		jdPW[i] = (jdPW[i-1] * 1LL * jd) % mod;
	}
	//brute_force();
	kwadraciak();
}