Analysis code
Routine questions, but there's a pit

int __cdecl main(int argc, const char **argv, const char **envp)
{
  char v3; // al
  __int64 v5; // [rsp+0h] [rbp-40h]
  int i; // [rsp+4h] [rbp-3Ch]
  FILE *stream; // [rsp+8h] [rbp-38h]
  char filename[8]; // [rsp+10h] [rbp-30h]
  unsigned __int64 v9; // [rsp+28h] [rbp-18h]
 
  v9 = __readfsqword(0x28u);
  LODWORD(v5) = 0;
  while ( (signed int)v5 < strlen(s) )
  {
    if ( v5 & 1 )
      v3 = 1;
    else
      v3 = -1;
    *(&t + (signed int)v5 + 10) = s[(signed int)v5] + v3;
    LODWORD(v5) = v5 + 1;
  }
  strcpy(filename, "/tmp/flag.txt");
  stream = fopen(filename, "w");
  fprintf(stream, "%s\n", u, v5);
  for ( i = 0; i < strlen(&t); ++i )
  {
    fseek(stream, p[i], 0);
    fputc(*(&t + p[i]), stream);
    fseek(stream, 0LL, 0);
    fprintf(stream, "%s\n", u);
  }
  fclose(stream);
  remove(filename);
  return 0;
}

Analysis of key points:

LODWORD(v5) = 0;
  while ( (signed int)v5 < strlen(s) )
  {
    if ( v5 & 1 )
      v3 = 1;
    else
      v3 = -1;
    *(&t + (signed int)v5 + 10) = s[(signed int)v5] + v3;
    LODWORD(v5) = v5 + 1;
  }

Look at the values of s and t variables.

s:

.data:00000000006010A0 s
db 'c61b68366edeb7bdce3c6820314b7498',0

t:

.data:00000000006010E1
aHarifctf???
db 'harifCTF{???}',0

Please watch carefully, t's code composition

python script:

s='c61b68366edeb7bdce3c6820314b7498'

t1='harifCTF{????????????????????????????????}'

t=[]

for x in t1:
    t.append(x)

v6=0

while v6<len(s):
    if v6&1:
        v3=1
    else:
        v3=-1

    t[v6+10]=str(chr(ord(s[v6])+v3))
    
    v6=v6+1
    
flag=''

for x in t:
    flag+=x

    print (flag)

Make a mistake.

There was a pit.
Watch the topic
SharifCTF 2016

And S is missing in t.

No wonder I've been counting fewer than ten. I can't match it.

It was deliberately hidden.

Add S

It's OK.
.

ps: Experience: Strictly remember the form of flag! Find or guess the answer according to the form!