import streamlit as st

def authenticate():
    st.sidebar.title("Login")
    username = st.sidebar.text_input("Username", key="username")
    password = st.sidebar.text_input("Password", type="password", key="password")
    
    if username == "admin" and password == "admin":
        return True
    elif username and password:
        st.sidebar.error("Invalid credentials")
    
    return False

authenticated = authenticate()

if authenticated:
    st.title("Simple Greeting App")
    name = st.text_input("Enter your name:")
    if name:
        st.write(f"Hello {name}")
else:
    st.warning("Please log in to access the app.")