Conditions

from flask import Flask, request, render_template, render_template_string, redirect
import subprocess
import urllib
flag = open('flag.txt').read()
app = Flask(__name__)
@app.route('/')
def main():
    return redirect('/login')

@app.route('/login',methods=['GET','POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    elif request.method == 'POST':
        if len(request.values["username"]) >= 40:
            return render_template_string("Username is too long!")
        elif len(request.values["username"].upper()) <= 50:
            return render_template_string("Username is too short!")
        else:
            return flag
if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8000)

data = 'ßßßßßßßßßßßßßßßßßßßßßßßßßß'
print(len(data)) # display 26
print(len(data.upper())) # display 52