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

typedef struct
{
    int top;
    int items[100];
} Stack;
void initialize(Stack *s)
{
    s->top=0;
}
void push(Stack *s,int value)
{
    s->items[s->top++]=value;
}
int pop(Stack *s)
{
    return s->items[--s->top];
}
int isfull(Stack *s)
{
    return s->top<100?0:1 ;
}
int isempty(Stack *s)
{
    return s->top==0?1:0;
}

int postfix(char str[])
{
    Stack s;
    initialize(&s);
    int i;
    for (i=0; i<strlen(str); i++)
    {
        if (str[i]==' ')
            continue;
        if (str[i]<='9' && str[i]>='0')
            push(&s,str[i]-'0');
        else
        {
            int a,b;
            if (isempty(&s))
                printf("error.\n\n");
            else
                a=pop(&s);
            if (isempty(&s))
                printf("error.\n");
            else b=pop(&s);
            switch(str[i])
            {
            case '+':
                push(&s,b+a);
                break;
            case '-':
                push(&s,b-a);
                break;
            case '*':
                push(&s,b*a);
                break;
            case '/':
                push(&s,b/a);
                break;
            default:
                printf("error.\n");
            }
        }
    }
    return pop(&s);
}
int main()
{
    char str[20];
    gets(str);
    printf("\n\n%s=%d",str,postfix(str));
    return 0;
}