Computercraft gps maker

print("x ?")
x = read()
print("y ?")
y = read()
print("z ?")
z = read()
if fs.exists == "startup" then
    shell.run("rm startup")
end
f = fs.open("startup", "w")
f.writeLine('shell.run("gps host '..x..' '..tostring(tonumber(y)-1)..' '..z..'")')
f.close()
os.reboot()