forecasting

[babu]

Hi

i am working on GDP forecasting by using ARIMA MODELING.So i transform the data by using first difference logrithm.Now i got the forecasting results.But after transformation data is changed So i want to bring the data back to its origional form.I used follow transformation

d(log(gdp))=log(gdp)-log(gdp)(-1)
I dont know how to bring data back to its normal value after forecasting
Could anybody help me to solve this problem.thanks