void setup()
{
  volatile char *dirf,*outf;
  volatile char *dirk,*ink;
  dirf=0x30; outf=0x31;
  dirk=0x107; ink=0x106;
  *dirf=0xFF; *ink=0x00;
  volatile char switches;
  volatile long arr1[]={63,6,91,79,102,109,125,7,127};
  volatile long arr2[]={0,1,2,4,8,16,32,64,128};
  unsigned long sum=0,num,res[4];
  volatile long i,j,k,l,n,m,p,q,add;
loop:while(1)
  {
    sum=0;
    num=0;
    *outf=0;
    switches=*ink;
    for(i=1;i<=8;i++)
    {
      if((switches & arr2[i]) == arr2[i])//enter 1st digit of number
      {
        res[0]=i;//store 1st digit in array
        for(n=0;n<=50000;n++);//delay for debouncing
        while(1)
        {
          switches=*ink;
          for(j=1;j<=8;j++)
          {
            if((switches & arr2[j]) == arr2[j])//enter 2nd digit of number
            {
              res[1]=j;//store second digit in array
              for(n=0;n<=50000;n++);//delay for debouncing
              while(1)
              {
                switches=*ink;
                for(k=1;k<=8;k++)
                {
                  if((switches & arr2[k]) == arr2[k])//enter 3rd digit of number
                  {
                    res[2]=k;//store third digit in array
                    for(n=0;n<=50000;n++);//delay for debouncing
                    while(1)
                    {
                      switches=*ink;
                      for(l=1;l<=8;l++)
                      {
                        if((switches & arr2[l]) == arr2[l])//enter 4th digit of number
                        {
                          res[3]=l;//store fourth digit in array
                          for(n=0;n<=50000;n++);//delay for debouncing
                          for(p=0;p<=3;p++)
                          {
                            sum=sum+res[p];//sum of digits of number
                          }
                          add=sum;
                          if(add>9)// is sum is not a single digit
                          {
                            while(add!=0)
                            {
                              num=num+(add%10);
                              add=add/10;
                            }
                            if(num<10)//if sum is in single digit
                            {
                              for(l=1;l<=8;l++)
                              {
                                if(l==num)//compare index and num(sum)
                                {
                                  *outf=arr1[l];//display sum of digits
                                  for(volatile long h=0;h<=900000;h++);//delay
                                  goto loop;
                                }
                              }
                            }
                          }
                          else{
                            for(q=1;q<=8;q++)
                            {
                              *outf=arr1[q];
                              goto loop;
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
}

void loop()
{

}