#include <stdio.h>
#include <string.h>
#import <Foundation/NSData.h>
#import <Foundation/NSValue.h>
#import <Foundation/NSArray.h>

int  main()  {
  int c,err;
  double x,y;
  char *p,*q;
  NSMutableData *line = [NSMutableData new];
  NSMutableArray *stk = [NSMutableArray new];
#define POP(z)  z = [[stk lastObject] doubleValue]; \
                    [stk removeLastObject]
  while ((c=getchar())!=EOF)  {
    if (c=='\n' || c=='\r')  c = 0;
    [line appendBytes:(void*)&c length:1];
    if (c)  continue;
    [stk removeAllObjects];
    p = [line mutableBytes];
    err = 0;
    while (NULL!=(q=strtok(p," \t")))  {
      x = strtod(q,&p);  err = p!=q+strlen(q);
      p = NULL;
      if (err)  {
        err = q[1] || NULL==strchr("+-*/",*q) || 2>[stk count];
        if (err)  break;
        POP(y);  POP(x);
        switch (*q)  {
          case '+': x += y; break;
          case '-': x -= y; break;
          case '*': x *= y; break;
          case '/': x /= y;
        }
      }
      [stk addObject:[NSNumber numberWithDouble:x]];
    }
    if (err || 1<[stk count])  puts("error");
    else  if ([stk count])  {POP(x);  printf("%f\n",x);}
    [line setLength:0];
  }
  return  0;
}