n1=int(input('enter first number:'))
n2=int(input('enter second number:'))
n3=int(input('enter third number:'))
if n1>=n2 and n1>=n3:
    maxi=n1
elif n2>=n1 and n2>=n3:
    maxi=n2
else:
    maxi=n3
print('maximum value is',maxi)

(OR)

# using ternary operator

maxi=n1 if n1>=n2 else n2
maxi= maxi if maxi>=n3 else n3
print('maximum value is',maxi)