package main

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

const VALUE = "value"
const SERIES = "series"
const PARALLEL = "parallel"

type Operation struct {
	operator string
	value    int
	operands []*Operation
	parent   *Operation
}

func (op *Operation) addOperand(other *Operation) {
	op.operands = append(op.operands, other)
}

func (op *Operation) setOperator(diagramItem string) {
	if diagramItem == "[" {
		op.operator = PARALLEL
	} else if diagramItem == "(" {
		op.operator = SERIES
	}
}

func (op *Operation) compute() float64 {
	if op.operator == VALUE {
		return float64(op.value)
	}
	var operandValues []float64
	for _, operation := range op.operands {
		operandValues = append(operandValues, operation.compute())
	}
	sum := 0.0
	if op.operator == SERIES {
		for _, value := range operandValues {
			sum += value
		}
	} else {
		for _, value := range operandValues {
			sum += 1 / value
		}
		sum = 1 / sum
	}
	return sum
}

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]byte, 1000000), 1000000)

	var N int
	scanner.Scan()
	fmt.Sscan(scanner.Text(), &N)

	resistors := make(map[string]int)
	for i := 0; i < N; i++ {
		var name string
		var R int
		scanner.Scan()
		fmt.Sscan(scanner.Text(), &name, &R)
		resistors[name] = R
	}
	scanner.Scan()
	circuit := strings.Split(scanner.Text(), " ")
	mainOperation := &Operation{}
	mainOperation.setOperator(circuit[0])
	currentOperation := mainOperation
	for _, item := range circuit[1:] {
		if item == "[" || item == "(" {
			newOp := &Operation{parent: currentOperation}
			currentOperation = newOp
			currentOperation.setOperator(item)
		} else if item == "]" || item == ")" {
			if currentOperation != mainOperation {
				currentOperation.parent.addOperand(currentOperation)
				currentOperation = currentOperation.parent
			}
		} else {
			value := resistors[item]
			valueOp := &Operation{operator: VALUE, value: value, parent: currentOperation}
			currentOperation.addOperand(valueOp)
		}
	}

	fmt.Printf("%.1f\n", mainOperation.compute())
}