rednet:347: positive number expected

So i was makeing a program named gmail using rednet and had lots of errors. I fixed a few of them, but i couldn't solve this one.

print("Gmail")
print("-------------")
print("a) Send")
print(":)/>/> Receive")
print("-------------")
print("Choose:")
ab = read()
if ab == "a" then
rednet.open("right")
print("Insert Computer ID:")
id = read()
print("Insert Text:")
txt = read()
rednet.send(id, txt)
print("Sent")
sleep(2)
shell.run("gmail")
else
rednet.open("right")
rednet.receive()
end

There is someting wrong at

rednet.send(id, txt)

I guess?

rednet.send(id, text) – Id requires too be a number. read() returns a string.

fix:

id = tonumber(read())

Where should I put
id = tonumber(read())
?

by insert computer id

print("Gmail")
print("-------------")
print("a) Send")
print(":)/>/> Receive")
print("-------------")
print("Choose:")
ab = read()
if ab == "a" then
rednet.open("right")
print("Insert Computer ID:")
id = tonumber(read()) --this is the line where you need to turn it into a number
print("Insert Text:")
txt = read()
rednet.send(id, txt)
print("Sent")
sleep(2)
shell.run("gmail")
else
rednet.open("right")
rednet.receive()
end

tnx so much