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import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

public class cnf {

    static String readInput() throws IOException {
        BufferedInputStream bis = new BufferedInputStream(System.in);
        ByteArrayOutputStream buf = new ByteArrayOutputStream();
        int result = bis.read();
        while (result != -1) {
            buf.write((byte) result);
            result = bis.read();
        }
        return buf.toString();
    }

    static class Formula {

        Set<Set<Integer>> clauses = new HashSet<>();
        Set<Integer> hiddenVars = new HashSet<>();

        public Formula() {
            this.hiddenVars = new HashSet<>();
        }

        public Formula(Set<Integer> hiddenVars) {
            this.hiddenVars = hiddenVars;
        }

        Set<Integer> allVars() {
            Set<Integer> all = new HashSet<>();
            for (Set<Integer> clause : clauses) {
                all.addAll(clause.stream().map(Math::abs).collect(Collectors.toSet()));
            }
            return all;
        }

        @Override
        public String toString() {
            return clauses + ":" + hiddenVars;
        }
    }

    static Formula parseFormula(String input) {
        Pattern formulaPattern = Pattern.compile("\\(([^\\(\\)]+)\\)");
        Pattern clausePattern = Pattern.compile("~?x\\d+");

        Matcher formulaMatcher = formulaPattern.matcher(input);
        Formula formula = new Formula();

        while (formulaMatcher.find()) {
            Matcher clauseMatcher = clausePattern.matcher(formulaMatcher.group(1));

            Set<Integer> clause = new HashSet<>();

            while (clauseMatcher.find()) {
                String token = clauseMatcher.group(0);
                String[] tArray = token.split("x");
                int variable = Integer.parseInt(tArray[tArray.length - 1]) - 1;
                if (tArray[0].equals("~")) variable = -variable;
                clause.add(variable);
            }
            formula.clauses.add(clause);
        }

        return formula;
    }

    static Formula simplify(Formula formula) {
        boolean modified = false;
        Formula simplified = new Formula(formula.hiddenVars);
        for (Set<Integer> clause : formula.clauses) {
            if (clause.size() == 1) {
                int var = clause.iterator().next();
                simplified.hiddenVars.remove(Math.abs(var));
                for (Set<Integer> c2 : formula.clauses) {
                    if (c2.contains(var)) {
                        simplified.hiddenVars.addAll(c2.stream().map(Math::abs).collect(Collectors.toSet()));
                        simplified.hiddenVars.remove(Math.abs(var));
                        modified = true;
                    } else if (c2.contains(-var)) {
                        Set<Integer> moved = new HashSet<>(c2);
                        moved.remove(-var);
                        simplified.clauses.add(moved);
                        modified = true;
                    } else {
                        simplified.clauses.add(c2);
                    }
                }
                break;
            }
        }
        if (!modified) simplified = formula;
        Iterator<Set<Integer>> it = simplified.clauses.iterator();
        while (it.hasNext()) {
            if (it.next().isEmpty()) it.remove();
        }
        if (modified) {
            return simplify(simplified);
        } else {
            formula.hiddenVars.removeAll(formula.allVars());
            return simplified;
        }
    }

    static Formula normalize(Formula formula) {
        Map<Integer, Integer> m = new HashMap<>();
        int next = 0;
        for (Set<Integer> c : formula.clauses) {
            for (int v : c) {
                if (!m.keySet().contains(Math.abs(v))) m.put(Math.abs(v), next++);
            }
        }
        Formula normalized = new Formula();
        for (Set<Integer> c : formula.clauses) {
            Set<Integer> newClause = new HashSet<>();
            for (int v : c) {
                boolean positive = v > 0;
                int mapped = m.get(Math.abs(v));
                newClause.add(positive ? mapped : -mapped);
            }
            normalized.clauses.add(newClause);
        }
        normalized.hiddenVars = formula.hiddenVars;
        return normalized;
    }

    static boolean eval(Formula formula, BigInteger values) {
        boolean formulaEval = true;
        for (Set<Integer> clause : formula.clauses) {
            boolean clauseEval = false;
            for (int var : clause) {
                boolean negate = var < 0;
                var = Math.abs(var);
                boolean varEval = values.testBit(var);
                if (negate) varEval = !varEval;
                clauseEval |= varEval;
            }
            formulaEval &= clauseEval;
        }
        return formulaEval;
    }

    static int countTrueConfigurations(Formula formula) {
        BigInteger loopBoundary = BigInteger.valueOf(2).pow(formula.allVars().size());
        BigInteger i = BigInteger.ZERO;
        BigInteger counter = BigInteger.ZERO;
        while (i.compareTo(loopBoundary) < 0) {
            if (eval(formula, i)) counter = counter.add(BigInteger.ONE);
            i = i.add(BigInteger.ONE);
        }
        counter = counter.multiply(BigInteger.valueOf(2).pow(formula.hiddenVars.size()));
        counter = counter.mod(BigInteger.valueOf(1000000007));
        return counter.intValue();
    }

    public static void main(String[] args) throws IOException {
        String[] input = readInput().split("\n");
//        System.out.println(Arrays.toString(input));
        Formula formula = parseFormula(input[1]);

//        System.out.println(formula);

        formula = normalize(simplify(formula));

//        System.out.println(formula);

        System.out.println(countTrueConfigurations(formula));
    }

}