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.model small
.stack 256
.data   
public flag
    msg1 db 'Enter string: $'
    msg2 db 13, 10, 'Result: $'
    msg3 db 13, 10, 'Substring found$'
    max_size db 255
    real_size db ?
    string db 255 dup (?)
    flag db 0
    
extrn PrintStr:near
extrn ReadStr:near
extrn Change:near
 
.code   
assume cs:@code
start:
    mov ax,@data
    mov ds,ax
    mov es, ax
    
    mov dx, offset msg1
    call PrintStr
    mov dx, offset max_size
    call ReadStr
    
    mov di, offset string
    call change
    
    mov dx, offset msg2
    call PrintStr
    mov dx, offset string
    call PrintStr
    cmp flag, 0
    je exit
    mov dx, offset msg3
    call PrintStr
exit:   
    mov ax, 4c00h
    int 21h
end start

.model small
public ReadStr
.code
ReadStr proc
    push ax
    mov ah, 10
    int 21h
    pop ax
    ret
ReadStr endp
end

.model small
public WriteStr
.code
WriteStr proc
    push ax
    mov ah, 9
    int 21h
    pop ax
    ret
WriteStr endp
end

.model small
public Change
extrn flag:byte
.code
Change proc
    push si
    push di
    push ax
    mov si, di
@@1:
    lodsb
    cmp al, 13
    je ok
    cmp al, 'e'
    jne @@2
    cmp word ptr [si], 'ee'
    jne @@2
    mov al, 'o'
    add si, 2
    mov flag, 1
@@2:
    stosb
    loop @@1
ok:
    mov al, '$'
    stosb
    pop ax
    pop di
    pop si
    ret
Change endp
end

PrintStr PROTO 
ReadStr PROTO
Change PROTO

extrn PrintStr PROTO 
extrn ReadStr PROTO
extrn Change PROTO

PrintStr PROTO 
ReadStr PROTO
Change PROTO

Change proc far