# Write a function that takes a string
# replace every even position of characters in string
# with "@^-^@" and return the modified string



def modify_string(string):
    result = ""

    for i in range(len(string)):
        if i % 2 == 0:
            result += "@^-^@"
        else:
            result += string[i]

    return result


print(modify_string("introduction to python"))