ASM2 challenge source from zh3r0 CTF 2020

ASM2.asm

start(int, int):
        push    rbp
        mov     rbp, rsp
        sub     rsp, 48
        mov     DWORD PTR [rbp-36], edi
        mov     DWORD PTR [rbp-40], esi
        mov     eax, DWORD PTR [rbp-36]
        mov     edi, eax
        call    f(int)
        mov     DWORD PTR [rbp-4], eax
        mov     eax, DWORD PTR [rbp-40]
        mov     edi, eax
        call    f(int)
        mov     DWORD PTR [rbp-8], eax
        mov     DWORD PTR [rbp-12], 0
        mov     DWORD PTR [rbp-16], 0
.L3:
        cmp     DWORD PTR [rbp-4], 0
        jle     .L2
        mov     edx, DWORD PTR [rbp-4]
        movsx   rax, edx
        imul    rax, rax, 1717986919
        shr     rax, 32
        mov     ecx, eax
        sar     ecx, 2
        mov     eax, edx
        sar     eax, 31
        sub     ecx, eax
        mov     eax, ecx
        sal     eax, 2
        add     eax, ecx
        add     eax, eax
        mov     ecx, edx
        sub     ecx, eax
        mov     esi, DWORD PTR [rbp-4]
        movsx   rax, esi
        imul    rax, rax, 1717986919
        shr     rax, 32
        mov     edx, eax
        sar     edx, 2
        mov     eax, esi
        sar     eax, 31
        sub     edx, eax
        mov     eax, edx
        sal     eax, 2
        add     eax, edx
        add     eax, eax
        sub     esi, eax
        mov     edx, esi
        mov     eax, ecx
        imul    eax, edx
        add     DWORD PTR [rbp-12], eax
        mov     eax, DWORD PTR [rbp-4]
        movsx   rdx, eax
        imul    rdx, rdx, 1717986919
        shr     rdx, 32
        sar     edx, 2
        sar     eax, 31
        sub     edx, eax
        mov     eax, edx
        mov     DWORD PTR [rbp-4], eax
        jmp     .L3
.L2:
        cmp     DWORD PTR [rbp-8], 0
        jle     .L4
        mov     edx, DWORD PTR [rbp-8]
        movsx   rax, edx
        imul    rax, rax, 1717986919
        shr     rax, 32
        mov     ecx, eax
        sar     ecx, 2
        mov     eax, edx
        sar     eax, 31
        sub     ecx, eax
        mov     eax, ecx
        sal     eax, 2
        add     eax, ecx
        add     eax, eax
        mov     ecx, edx
        sub     ecx, eax
        mov     esi, DWORD PTR [rbp-8]
        movsx   rax, esi
        imul    rax, rax, 1717986919
        shr     rax, 32
        mov     edx, eax
        sar     edx, 2
        mov     eax, esi
        sar     eax, 31
        sub     edx, eax
        mov     eax, edx
        sal     eax, 2
        add     eax, edx
        add     eax, eax
        sub     esi, eax
        mov     edx, esi
        mov     eax, ecx
        imul    eax, edx
        add     DWORD PTR [rbp-16], eax
        mov     eax, DWORD PTR [rbp-8]
        movsx   rdx, eax
        imul    rdx, rdx, 1717986919
        shr     rdx, 32
        sar     edx, 2
        sar     eax, 31
        sub     edx, eax
        mov     eax, edx
        mov     DWORD PTR [rbp-8], eax
        jmp     .L2
.L4:
        mov     DWORD PTR [rbp-20], 0
        mov     DWORD PTR [rbp-24], 1
.L8:
        cmp     DWORD PTR [rbp-24], 99
        jg      .L5
        mov     DWORD PTR [rbp-28], 1
.L7:
        cmp     DWORD PTR [rbp-28], 99
        jg      .L6
        mov     eax, DWORD PTR [rbp-12]
        imul    eax, DWORD PTR [rbp-24]
        mov     edx, eax
        mov     eax, DWORD PTR [rbp-16]
        imul    eax, DWORD PTR [rbp-28]
        add     eax, edx
        add     DWORD PTR [rbp-20], eax
        add     DWORD PTR [rbp-28], 1
        jmp     .L7
.L6:
        add     DWORD PTR [rbp-24], 1
        jmp     .L8
.L5:
        mov     eax, DWORD PTR [rbp-20]
        leave
        ret
f(int):
        push    rbp
        mov     rbp, rsp
        push    rbx
        sub     rsp, 24
        mov     DWORD PTR [rbp-20], edi
        cmp     DWORD PTR [rbp-20], 0
        jne     .L11
        mov     eax, 0
        jmp     .L12
.L11:
        cmp     DWORD PTR [rbp-20], 1
        jne     .L13
        mov     eax, 1
        jmp     .L12
.L13:
        mov     eax, DWORD PTR [rbp-20]
        sub     eax, 1
        mov     edi, eax
        call    f(int)
        mov     ebx, eax
        mov     eax, DWORD PTR [rbp-20]
        sub     eax, 2
        mov     edi, eax
        call    f(int)
        add     eax, ebx
.L12:
        add     rsp, 24
        pop     rbx
        pop     rbp
        ret