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

#define MAXOP 100
#define NUMBER '0'
#define MAXVAL 100
#define BUFSIZE 100
#define MAXLINE 1000

int getop(char []);
int getsop(char [], char []);
void push(double);
double pop(void);
int getch(void);
void ungetch(int);
int getline(char *, int);

int sp = 0;
double val[MAXVAL];
int buf[BUFSIZE];
int bufp = 0;
double p;
float vars[26];

int main(void) {
     int type;
     double op2;
     char s[MAXOP];
     char line[MAXLINE] = "\0";

     while ((type = getsop(s, line)) != EOF) {
	  switch (type) {
	  case NUMBER:
	       push(atof(s));
	       break;
	  case '+':
	       push(pop() + pop());
	       break;
	  case '-':
	       push(pop() - pop());
	       break;
	  case '*':
	       push(pop() * pop());
	       break;
	  case '/':
	       op2 = pop();
	       if (op2 != 0.0)
		    push(pop() / op2);
	       else
		    printf("error: zero divisor\n");
	       break;
	  case '%':
	       op2 = pop();
	       if (op2 != 0.0)
		    push(fmod(pop(), op2));
	       else
		    printf("error zero divisor\n");
	       break;
	  case 'd':
	       push(p);
	       break;
	  case 'a':
	       pop();
	       op2 = pop();
	       push(p);
	       push(op2);
	       break;
	  case 'p':
	       printf("\t%.8g\n", p);
	       break;
	  case 's':
	       push(sin(pop()));
	       break;
	  case 'e':
	       push(exp(pop()));
	       break;
	  case 'w':
	       push(pow(pop(), pop()));
	       break;
	  case 'c':
	       sp = 0;
	       break;
	  case 'r':
	       push(p);
	       break;
	  case '=':
	       if (isalpha((int) (op2 = pop()))) {
		    vars[(int) op2] = pop();
	       }
	       break;
	  case '\n':
	       printf("\t%.8g\n", pop());
	       break;
	  default:
	       if (isalpha(type)) {
		    if (vars[type] != 0) {
			 push(vars[type]);
		    } else {
			 push(type);
		    }
		    break;
	       }
	       printf("error: unknown command %s\n", s);
	       printf("type: %d\n", type);
	       break;
	  }
     }
     return 0;
}

void push(double f) {
     
     if (sp < MAXVAL) {
	  val[sp++] = f;
	  p = 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[]) {
     int i, c, sign = 1;

     while ((s[0] = c = getch()) == ' '|| c == '\t');
     s[1] = '\0';
     if (!isdigit(c) && c != '.' && c != '-')
	  return c;
     if (c == '-') {
	  if (isdigit(c=getch()))
	       sign = -1;
	  else {
	       ungetch(c);
	       return '-';
	  }
     }
     i = 0;
     if (sign < 0)
	  s[++i] = c;
     if (isdigit(c))
	  while (isdigit(s[++i] = c = getch()));
     if (c == '.')
	  while (isdigit(s[++i] = c = getch()));
     s[i] = '\0';
     if (c != EOF)
	  ungetch(c);
     return NUMBER;
}

int getch(void) {
     
     return (bufp > 0) ? buf[--bufp] : getchar();
}

void ungetch(int c) {

     if (bufp >= BUFSIZE)
	  printf("ungetch: too many characters\n");
     else
	  buf[bufp++] = c;
}

void ungets(char s[]) {
     int i;

     for (i = 0; s[i] != '\0'; i++)
	  ungetch(s[i]);
}

int buffer = (int) NULL;

int getch1(void) {
     int c;

     if (buffer == (int) NULL)
	  return getchar();
     else {
	  c = buffer;
	  buffer = (int) NULL;
	  return c;
     }
}

void ungetch1(int c) {

     if (buffer == (int) NULL)
	  buffer = c;
     else
	  printf("AIEEEE!\n");
}

int getsop(char s[], char t[]) {
     int i, c, sign = 1;
     static int j;

     if (t[j] == '\0') {
	  getline(t, MAXLINE);
	  j = 0;
     }
     while ((s[0] = c = t[j++]) == ' '|| c == '\t');
     s[1] = '\0';
     if (!isdigit(c) && c != '.' && c != '-')
	  return c;
     if (c == '-') {
	  if (isdigit(c=t[j++]))
	       sign = -1;
	  else {
	       j--;
	       return '-';
	  }
     }
     i = 0;
     if (sign < 0)
	  s[++i] = c;
     if (isdigit(c))
	  while (isdigit(s[++i] = c = t[j++]));
     if (c == '.')
	  while (isdigit(s[++i] = c = t[j++]));
     s[i] = '\0';
     if (c != EOF)
	  j--;
     return NUMBER;
}

int getline(char *s, int len) {
     char c;
     int i;

     for (i = 0; i < len-1 && (c = getchar()) != EOF && c != '\n'; i++)
	  s[i] = c;
     if (c == EOF)
	  s[i++] = c;
     else if (c == '\n')
	  s[i++] = '\n';
     s[i++] = '\0';

     return i;
} /* getline() */

int shitop(char s[]) {
     int i, c, sign = 1;
     int last = 0;

     if (last == 0) {
	  c = getch();
     } else {
	  c = last;
	  last = 0;
     }
     while ((s[0] = c) == ' '|| c == '\t');
     s[1] = '\0';
     if (!isdigit(c) && c != '.' && c != '-')
	  return c;
     if (c == '-') {
	  if (isdigit(c=getch()))
	       sign = -1;
	  else {
	       last = c;
	       return '-';
	  }
     }
     i = 0;
     if (sign < 0)
	  s[++i] = c;
     if (isdigit(c))
	  while (isdigit(s[++i] = c = getch()));
     if (c == '.')
	  while (isdigit(s[++i] = c = getch()));
     s[i] = '\0';
     if (c != EOF)
	  last = c;
     return NUMBER;
}