String hidden inside .s assembly source code - gcc

Question

I've been really stuck with a challenge at our "hacking" class. A string (password) needs to be found, and the only file provided is a .s assembly file.
Based on my extremely small knowledge of assembly, I compiled the file with gcc -S Program.s, with an a.outexecutable file being output. I tried to run the file with ./a.out in Mac Terminal, to no success — after pressing enter at the end of the command, cursor just jumps to a new line with nothing in stdout, and echo $? returns 0.
At the end of the assembly file, there's a .asciz "zja4heit5k7", so I figured it might be the correct string, but to no success.
I would be eternally thankful if anyone can provide any steps to help me solve the problem.
Program.s
.
.section __TEXT,__text,regular,pure_instructions
.macosx_version_min 10, 13
.globl _r
.p2align 4, 0x90
_r: ## #r
.cfi_startproc
## BB#0:
pushq %rbp
Lcfi0:
.cfi_def_cfa_offset 16
Lcfi1:
.cfi_offset %rbp, -16
movq %rsp, %rbp
Lcfi2:
.cfi_def_cfa_register %rbp
movq %rdi, -8(%rbp)
movl $0, -12(%rbp)
movl $0, -12(%rbp)
LBB0_1: ## =>This Inner Loop Header: Depth=1
xorl %eax, %eax
movb %al, %cl
cmpq $0, -8(%rbp)
movb %cl, -13(%rbp) ## 1-byte Spill
je LBB0_3
## BB#2: ## in Loop: Header=BB0_1 Depth=1
movq -8(%rbp), %rax
movslq -12(%rbp), %rcx
movsbl (%rax,%rcx), %edx
cmpl $0, %edx
setne %sil
movb %sil, -13(%rbp) ## 1-byte Spill
LBB0_3: ## in Loop: Header=BB0_1 Depth=1
movb -13(%rbp), %al ## 1-byte Reload
testb $1, %al
jne LBB0_4
jmp LBB0_9
LBB0_4: ## in Loop: Header=BB0_1 Depth=1
movq -8(%rbp), %rax
movslq -12(%rbp), %rcx
movsbl (%rax,%rcx), %edx
cmpl $97, %edx
jl LBB0_7
## BB#5: ## in Loop: Header=BB0_1 Depth=1
movq -8(%rbp), %rax
movslq -12(%rbp), %rcx
movsbl (%rax,%rcx), %edx
addl $13, %edx
cmpl $122, %edx
jg LBB0_7
## BB#6: ## in Loop: Header=BB0_1 Depth=1
movq -8(%rbp), %rax
movslq -12(%rbp), %rcx
movsbl (%rax,%rcx), %edx
addl $13, %edx
movb %dl, %sil
movq -8(%rbp), %rax
movslq -12(%rbp), %rcx
movb %sil, (%rax,%rcx)
LBB0_7: ## in Loop: Header=BB0_1 Depth=1
jmp LBB0_8
LBB0_8: ## in Loop: Header=BB0_1 Depth=1
movl -12(%rbp), %eax
addl $1, %eax
movl %eax, -12(%rbp)
jmp LBB0_1
LBB0_9:
popq %rbp
retq
.cfi_endproc
.globl _main
.p2align 4, 0x90
_main: ## #main
.cfi_startproc
## BB#0:
pushq %rbp
Lcfi3:
.cfi_def_cfa_offset 16
Lcfi4:
.cfi_offset %rbp, -16
movq %rsp, %rbp
Lcfi5:
.cfi_def_cfa_register %rbp
subq $16, %rsp
leaq _an(%rip), %rdi
movl $0, -4(%rbp)
callq _r
xorl %eax, %eax
addq $16, %rsp
popq %rbp
retq
.cfi_endproc
.section __DATA,__data
.globl _an ## #an
_an:
.asciz "zja4heit5k7"
.subsections_via_symbols