#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

double end_of_expr(double a, double b) { return 0; }
double last_value(double a, double b) { return 0; }
double expr_add(double a, double b) { return a + b; }
double expr_sub(double a, double b) { return a - b; }
double expr_mul(double a, double b) { return a * b; }
double expr_div(double a, double b) { return a / b; }

void error(char *text)
{
    fprintf(stderr,"error: %s\n",text);
    exit(-2);
}

typedef struct PART
{
    double value;
    double (*operation)(double,double);
    int prior;
} PART;

PART eval(PART left, char **expr);
PART get_part(char **expr)
{
    char *start;
    PART part = {0,};

    while ( isspace(**expr) ) ++*expr;

    if ( **expr == ')' || !**expr )
    {
        part.operation = end_of_expr;
        if (**expr) ++*expr;
        return part;
    }

    if ( **expr == '(' )
    {
        ++*expr;
        part = eval(get_part(expr),expr);
    }
    else
    {
        start = *expr;
        part.value = strtod(start,expr);
        if ( *expr == start ) error("invalid value");
    }

    while ( isspace(**expr) ) ++*expr;

    if ( **expr == ')' || !**expr )
    {
        part.operation = last_value;
        return part;
    }

    switch ( **expr )
    {
        case '+': part.operation = expr_add; part.prior = 1; break;
        case '-': part.operation = expr_sub; part.prior = 1; break;
        case '*': part.operation = expr_mul; part.prior = 2; break;
        case '/': part.operation = expr_div; part.prior = 2; break;
        default:
            error("invalid operation");
    }
    ++*expr;
    return part;
}

PART eval(PART left, char **expr)
{
    PART right = get_part(expr);
    while ( right.operation != end_of_expr )
    {
        if ( left.prior >= right.prior )
        {
            right.value = left.operation(left.value,right.value);
            left = right;
            right = get_part(expr);
        }
        else
            right = eval(right, expr);
    }
    return left;
}

double calc(char *expr)
{
    char *expr_ptr = expr;
    return eval(get_part(&expr_ptr),&expr_ptr).value;
}

int main()
{
    int exprLen = 0;
    char expr[256];
    double result;

    for(;;)
    {
        fgets(expr,sizeof(expr),stdin);
        exprLen = strlen(expr);

        if ( !exprLen ) exit(0);
        if ( expr[exprLen-1] != '\n' )
        {
            fputs("expression truncated\n",stderr);
            exit(1);
        }

        result = calc(expr);
        printf("=> %f\n",result);
    }
}