You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: main.rs
    path of file: ./repos/risc0/templates/rust-starter/host/src
    
    the code of the file until where you have to start completion: // These constants represent the RISC-V ELF and the image ID generated by risc0-build.
// The ELF is used for proving and the ID is used for verification.
use methods::{
    {{guest_elf}}, {{guest_id}}
};
use risc0_zkvm::{default_prover, ExecutorEnv};

fn main() {
    // Initialize tracing. In order to view logs, run `RUST_LOG=info cargo run`
    tracing_subscriber::fmt()
        .with_env_filter(tracing_subscriber::filter::EnvFilter::from_default_env())
        .init();

    // An executor environment describes the configurations for the zkVM
    // including program inputs.
    // An default ExecutorEnv can be created like so:
    // `let env = ExecutorEnv::builder().build().unwrap();`
    // However, this `env` does not have any inputs.
    //
    // To add add guest input to the executor environment, use
    // ExecutorEnvBuilder::write().
    // To access this method, you'll need to use ExecutorEnv::builder(), which
    // creates an ExecutorEnvBuilder. When you're done adding input, call
    // ExecutorEnvBuilder::build().

    // For example:
    let input: u32 = 15 * u32::pow(2, 27) + 1;
    let env = ExecutorEnv::builder()
        .write(&input)
        .unwra
    
fn main() {
    // Initialize tracing. In order to view logs, run `RUST_LOG=info cargo run`
    tracing_subscriber::fmt()
        .with_env_filter(tracing_subscriber::filter::EnvFilter::from_default_env())
        .init();

    // An executor environment describes the configurations for the zkVM
    // including program inputs.
    // An default ExecutorEnv can be created like so:
    // `let env = ExecutorEnv::builder().build().unwrap();`
    // However, this `env` does not have any inputs.
    //
    // To add add guest input to the executor environment, use
    // ExecutorEnvBuilder::write().
    // To access this method, you'll need to use ExecutorEnv::builder(), which
    // creates an ExecutorEnvBuilder. When you're done adding input, call
    // ExecutorEnvBuilder::build().

    // For example:
    let input: u32 = 15 * u32::pow(2, 27) + 1;
    let env = ExecutorEnv::builder()
        .write(&input)
        .unwrap()
        .build()
        .unwrap();

    // Obtain the default prover.
    let prover = default_prover();

    // Produce a receipt by proving the specified ELF binary.
    let receipt = prover
        .prove(env, {{guest_elf}})
        .unwrap();

    // TODO: Implement code for retrieving receipt journal here.

    // For example:
    let _output: u32 = receipt.journal.decode().unwrap();

    // The receipt was verified at the end of proving, but the below code is an
    // example of how someone else could verify this receipt.
    receipt
        .verify({{guest_id}})
        .unwrap();
}