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.MODEL SMALL
.STACK 200H
.DATA
N1 DB ?
N2 DB ?
N3 DB ?   
N4 DB ?
M1 DB 'Enter 1st number: $'
M2 DB 'Enter 2nd number: $'
M3 DB 'Enter 3rd number: $'   
M4 DB 'Calculation of $'
M5 DB ', $'
M6 DB ' and $'
M7 DB ' is: $'
.CODE                      
MAIN PROC                  
    
    MOV AX,@DATA
    MOV DS,AX
    
    LEA DX,M1   
    MOV AH,9
    INT 21H
    
    MOV AH,1    ;input
    INT 21H
    MOV N1,AL         
    
    MOV AH,2    ;newline
    MOV DL,0DH
    INT 21H   
    MOV DL,0AH
    INT 21H    
    
    LEA DX,M2    
    MOV AH,9
    INT 21H
    
    MOV AH,1    ;input
    INT 21H
    MOV N2,AL         
    
    MOV AH,2    
    MOV DL,0DH
    INT 21H   
    MOV DL,0AH
    INT 21H 
    
    LEA DX,M3  
    MOV AH,9
    INT 21H
    
    MOV AH,1    ;input
    INT 21H
    MOV N3,AL         
    
    MOV AH,2    
    MOV DL,0DH
    INT 21H   
    MOV DL,0AH
    INT 21H     
    
    
    MOV BL,N1
    ADD BL,N2
    SUB BL,N3  
        
      
    LEA DX,M4
    MOV AH,9
    INT 21H 
    
    MOV AH,2
    MOV DL,N1
    INT 21H
    
    LEA DX,M5
    MOV AH,9
    INT 21H
    
    MOV AH,2
    MOV DL,N2
    INT 21H
    
    LEA DX,M6
    MOV AH,9
    INT 21H
    
    MOV AH,2
    MOV DL,N3
    INT 21H

    LEA DX,M7
    MOV AH,9
    INT 21H
    
    MOV AH,2 
    MOV DL,BL
    INT 21H

    MOV AL,0
    MOV AH,4CH
    INT 21H
    MAIN ENDP
END MAIN