input first gdp and rival gdp with first growth rate and the growth rate of your rival.
be careful first gdp must be lower than the gdp of the rival but first growth rate must be higher than growth rate of the rival.
the goal is to know when the first country will be able to catch up with the rival or rivals .
for example 2013:chine with its gdp (7000 billion dollars) and growth rate(7%) and usa with its gdp (16000 billion dollars) and growth rate (2.5).
china will catch up with usa after 20 years. CHINA:27087.791 billion dollars /USA:26217.863 billion dollars IN 2033 .