import pandas as pd 

df_items = pd.read_csv('items.csv')
df_signup = pd.read_csv('signup.csv')
df_signup1 = pd.read_csv('signup1.csv')

merged_signup = pd.concat([df_signup,df_signup1],ignore_index=True)
merged_df = pd.merge(df_items,merged_signup,on = 'item_id',how = 'left')
result = merged_df.groupby(['item_name'])['employee_id'].count()
print(result[result > 0])