括号匹配问题

#include <stdio.h>
#include <ctype.h>
#include <io.h>
#include <stdlib.h>
#include <process.h>
#include <malloc.h>
#include <limits.h>
#include <math.h>
#include <string.h>
#define TRUE 1
#define FALSE 0
#define OK 1
#define ERROR 0
#define INFEASIBLE -1
#define OVERFLOW -2
#define STACK_INIT_SIZE 100
#define STACKINCREMENT 10
typedef int SElemType;
typedef int Status;
typedef struct{
    SElemType *base;
    SElemType *top;
    int stacksize;
}Sqstack;
Status Initstack(Sqstack *S)
{
    S->base=(SElemType*)malloc(STACK_INIT_SIZE*sizeof(SElemType));
    if(!S->base)exit(OVERFLOW);
    S->top=S->base;
    S->stacksize=STACK_INIT_SIZE;
    return OK;
}
Status Destroystack(Sqstack *S)
{
    free(S->base);
    S->base=NULL;
    S->top=0;
    S->stacksize=0;
    return OK;
}
Status Gettop(Sqstack S,SElemType *e)
{
    if(S.top==S.base) return ERROR;
    e=S.top-1;
    return OK;
}

Status Push(Sqstack *S,SElemType e)
{
    if(S->top-S->base>=S->stacksize)
    {
        S->base=(SElemType*)realloc(S->base,(S->stacksize+STACKINCREMENT)*sizeof(SElemType));
        if(!S->base)exit(OVERFLOW);
        S->top=S->base+S->stacksize;
        S->stacksize+=STACKINCREMENT;
    }
    *S->top++=e;
return OK;
}
Status pop(Sqstack *S,SElemType *e)
{
    if(S->top==S->base) return ERROR;
    e=--S->top;
    return OK;
}
int main(void)
{
Sqstack S;
int e,j=0,b=0,c=0;   
char a;
Initstack(&S);
scanf("%s",&a);
Gettop(S,&e);
    switch(a)
        {
        case'(':Push(&S,e); ++j; break;
        case'{':Push(&S,e); ++b; break;
        case'[':Push(&S,e); ++c; break;
        case')':pop(&S,&e); --j; break;
        case'}':pop(&S,&e); --b; break;
        case']':pop(&S,&e); --c; break;
        default:    break;
            
        }
   
    if(j>=1||b>=1||c>=1)
    {
    printf("Extra left brackets\n");
    }
    else if(j<=-1||b<=-1||c<=-1)
    {
    printf("Extra right brackets\n");
    }

    else if(j==0&&b==0&&c==0)
    {
        printf("Brackets match\n");
    }
    else
    {
        printf("Brackets not match\n");
    }
    Destroystack(&S);

return 0;
}问题就是输出结果永远是Extra left brackets，可能是判断条件的问题有没有大佬解决一下咧