---

.model small
.stack 100h

.data
n       dw 25
result  dw 0

.code
start:

    mov ax, @data
    mov ds, ax

    mov cx, 100
    mov bx, 1

m1:
    mov ax, bx
    mul bx

    cmp ax, n
    je found

    inc bx

    loop m1

    mov result, 0
    jmp finish

found:
    mov result, bx

finish:
    mov ax, 4C00h
    int 21h

end start