by Dinesh Thakur

 
#include <stdio.h>

int main()
{
       int c, lbraces=0, rbraces=0, lb='{', rb='}';
     
       while ((c=getchar()) != EOF)
             {
                 putchar(c);
                 while (c==lb || c==rb)
                         {
                              if (c==lb) lbraces++;
                              if (c==rb) rbraces++;
                              if (rbraces > lbraces)
                                {
                                    printf("??");
                                    rbraces--;
                                }
                                    c=0;
                        }
            }
                  if (lbraces > rbraces)
                  printf(" %d missing ",lbraces-rbraces);
                  for (;lbraces > rbraces; lbraces--)
                  putchar(rb);
                  return 0;
}