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

struct stack{
    char data[100];
    int size;
}s;

void push(char ch){
    if(s.size < 100){
        s.size++;
        s.data[s.size] = ch;
    }
    else
        exit(0);
} 

void pop(){
    if(s.size >= 0)
        s.size--;
    else 
        exit(0);
}

bool find_pair(char a, char b){
    if(a == '(' && b == ')') 
        return true;
    if(a == '{' && b == '}')
        return true;
    if(a == '<' && b == '>')
        return true;
    if(a == '[' && b == ']')
        return true;

    return false;

}
char right_pair(char a){
    char b;
    if(a == '(')
        b = ')';
    if(a == '{')
        b = '}';
    if(a == '[')
        b = ']';
    if(a == '<')
        b = '>';

    return b;    
}

char gettop(){
    return s.data[s.size];
}

int main(){
    
    
    char line[100];
    s.size = -1;

    printf("Read: ");
    char *x = fgets(line, 100, stdin);
    printf("%s", line);

    int l = strlen(line);
    int i, j = -1;
    char *a = calloc(l, sizeof(char));
    char *b = calloc(l, sizeof(char));
     
    for(i = 0; i < l; i++){
        if(line[i] == '{' || line[i] == '(' || line[i] == '[' || line[i] == '<'){
            push(line[i]);
            j++;
            a[j] = gettop();
            b[j] = right_pair(a[j]);
        }
        if(line[i] == '}' || line[i] == ')' || line[i] == ']' || line[i] == '>'){   
            if(s.size == -1){
                printf("Unexpected closing bracket %c in %d\n", line[i], i);
                return 0; 

            }
           else if(!find_pair(gettop(), line[i])){
                printf("Crossed bracket %c in %d, expected %c\n", line[i], i, b[j]);
                return 0;            
            }
            else{
                 pop();
            }
        }
    }
    int begin = 0;
    int end = strlen(b);
    int h;
    while(begin < end){
        h = b[begin];
        b[begin++] = b[--end];
        b[end] = h;
    }

    if(s.size == -1){
        printf("All brackets OK\n");
    }
    else {
        printf("Missing closing brackets: %s \n", b);        
    }
    free(a);
    free(b);
    return 0;
}