import hashlib
import json

def main():
    data = {"step": 1, "value": "start"}
    for i in range(2, 6):
        h = hashlib.sha256(json.dumps(data).encode()).hexdigest()[:8]
        data = {"step": i, "prev_hash": h, "value": f"chain-{i}"}
    return json.dumps(data)