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

#define MAXOP 100
#define NUMBER '0'
#define MAXVAL 100

int getop(char []);
void push(double);
double pop(void);

int sp = 0;
double val[MAXVAL];

int main(void) {
     int type;
     double op2;
     char s[MAXOP];

     while ((type = getop(s)) != EOF) {
	  switch (type) {
	  case NUMBER:
	       push(atof(s));
	       break;
	  case '+':
	       push(pop() + pop());
	       break;
	  case '-':
	       op2 = pop();
	       push(pop() - op2);
	       break;
	  case '/':
	       op2 = pop();
	       if (op2 != 0.0)
		    push(pop() / op2);
	       else
		    printf("error: zero divisor\n");
	       break;
	  case 'p':
	       printf("\t%.8g\n", pop());
	       break;
	  default:
	       printf("error: unkown command %s\n", s);
	       break;
	  }
     }
     
     return 0;
}

void push(double f) {

     if (sp < MAXVAL)
	  val[sp++] = f;
     else
	  printf("error: stack full, can't push %g\n", f);
}

double pop(void) {

     if (sp > 0)
	  return val[--sp];
     else {
	  printf("error: stack empty\n");
	  return 0.0;
     }
}

int getop(char s[]) {

     scanf("%s", s);

     if (isdigit(s[0]))
	  return NUMBER;
     else if (s[0] == '.' && isdigit(s[1]))
	  return NUMBER;
     else
	  return s[0];
}