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

#define STACK_SIZE 20

struct stack{
    float values[STACK_SIZE];
    int size;
};

void print_stack(struct stack* stack);
void push_stack(struct stack* stack, float value);
float pop_stack(struct stack* stack);


int main(){
    

    char char_value[STACK_SIZE];
    memset(&char_value,0,STACK_SIZE);
    float float_value;
    char* ptr;
    struct stack myStack;
    memset(&myStack,0,sizeof(struct stack));
    while(1){
        ptr = fgets(char_value, STACK_SIZE-1, stdin);
        if(ptr != NULL){
            if(char_value[0] == '\n'){
                puts("no input");
                break;
            }

            /*if(char_value[0] == '0'){
                push_stack(&myStack,0);
                print_stack(&myStack);
                printf("\n");
                continue;
            }*/
 
            if(char_value[0] == '+'){
                    if(myStack.size > 1){
                    float a = pop_stack(&myStack);
                    float b = pop_stack(&myStack);                    
                    float c = a+b;
                    push_stack(&myStack, c);
                    print_stack(&myStack);
                    printf("\n");
                    }else{puts("not enough operands"); break;}
            }else if(char_value[0] == '-'){
                    if(myStack.size > 1){
                    float a = pop_stack(&myStack);
                    float b = pop_stack(&myStack);                    
                    float c = b-a;
                    push_stack(&myStack, c);
                    print_stack(&myStack);
                    printf("\n");
                    }else{puts("not enough operands"); break;}
                }else if(char_value[0] == '*'){
                    if(myStack.size > 1){
                    float a = pop_stack(&myStack);
                    float b = pop_stack(&myStack);                    
                    float c = a*b;
                    push_stack(&myStack, c);
                    print_stack(&myStack);
                    printf("\n");
                    }else{puts("not enough operands"); break;}
                } else if(char_value[0] == '/'){
                    if(myStack.size > 1){
                    float a = pop_stack(&myStack);
                    if(a == 0){
                        printf("division by zero\n");
                        break;
                    }else{
                        float b = pop_stack(&myStack);                    
                        float c = b/a;
                        push_stack(&myStack, c);
                        print_stack(&myStack);
                        printf("\n");
                    }
                    }else{puts("not enough operands"); break;}
                } else if(isdigit(char_value[0]) != 0 ){
                    float_value = strtof(char_value, NULL);
                    //printf("float value: %f\n",float_value);
                    /*if(float_value == 0){
                        puts("bad input");
                        break;*/
                    //} else {
                        push_stack(&myStack,float_value);
                        print_stack(&myStack);
                        printf("\n");
                        continue;
               
                } else {
                    puts("bad input");
                    break;
                }
        } else { 
               //push_stack(&myStack, float_value);
               //print_stack(&myStack);
               //printf("\n");
                puts("no input");
                break;
            }
        } 


    return 0;
}

void print_stack(struct stack* stack){
    for(int i = 0; i < stack->size; i++){
        printf("%.2f ",stack->values[i]);
    }
}

void push_stack(struct stack* stack, float value){
    assert(stack->size < STACK_SIZE);
    stack->values[stack->size] = value;
    stack->size += 1;
}

float pop_stack(struct stack* stack){
    assert(stack->size > 0);
    float value = stack->values[stack->size-1];
    stack->size -= 1;
    return value;
}