我想计算文本字段中整数的值，而忽略整数之前所需的文本字符串？

I am making my own assistant program that connects to a bank management program i wrote. I want the user to be able to type into the command field: add or add 500 or any other amount. How would i calculate the "10500" while ignoring the "add $". The "add $" is used to check what command the user is typing to perform the action. This is what i have so far.I am making my own assistant program that conne