Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Example Input: Context: Selenoproteins are an elite group of proteins containing a rare amino acid, selenocysteine (Sec), encoded by the codon, UGA. In eukaryotes, incorporation of Sec requires a Sec insertion sequence (SECIS) element, a stem-loop structure located in the 3'-untranslated regions of selenoprotein mRNAs. Here we report identification of a noncanonical form of SECIS element in Toxoplasma gondii and Neospora canine, single-celled apicomplexan parasites of humans and domestic animals. This SECIS has a GGGA sequence in the SBP2-binding site in place of AUGA previously considered invariant. Using a combination of computational and molecular techniques, we show that Toxoplasma and Neospora possess both canonical and noncanonical SECIS elements. The GGGA-type SECIS element supported Sec insertion in mammalian HEK 293 and NIH 3T3 cells and did so more efficiently than the natural mammalian SECIS elements tested. In addition, mammalian type I and type II SECIS elements mutated into the GGGA forms were functional but manifested decreased Sec insertion efficiency. We carried out computational searches for both AUGA and GGGA forms of SECIS elements in Toxoplasma and detected five selenoprotein genes, including one coding for a previously undescribed selenoprotein, designated SelQ, and two containing the GGGA form of the SECIS element. In contrast, the GGGA-type SECIS elements were not detected in mammals and nematodes. As a practical outcome of the study, we developed pSelExpress1, a vector for convenient expression of selenoproteins in mammalian cells. It contains an SBP2 gene and the most efficient tested SECIS element: an AUGA mutant of the GGGA-type Toxoplasma SelT structure. 
 Question: What is the name of the stem loop present in the 3' end of genes encoding for selenoproteins?
Example Output: secis

Example Input: Context: 2008 will be remembered by us Chinese people as a year of sadness and happiness. May of the year sadly saw the Great Sichuan Earthquake, the worst earthquake in China over 30 years. It killed around 70,000 people. Tens of thousands were injured or went missing. However, to our delight, China also hosted its first Olympic games that summer in Beijing. It was a very successful games with a great opening ceremony. 43 new world records and 132 new Olympic records were made. And China came out first with 51 gold medals. 
 Question: How many gold medals did China win at the 2008 Beijing Olympic Games?
Example Output: 51.

Example Input: Context: In a time when a dangerous number of people are overweight, many people seem to have forgotten the most important way to keep healthy and slim---exercise. And as a new study carried out on mice in the lab has shown, exercise done early in life can reward you in your adult years. A team of researchers at the University of California studied the effects of early exercise on adult physical activity, body mass and eating. They found that early-age exercise in mice has positive effects on adult levels of voluntary exercise in addition to reducing body mass. "These results may have an effect on the importance of regular physical education in elementary and middle schools," said Theodore Garland, a professor of biology, who led the research project. "If kids exercise regularly through their school years, then they may be more likely to exercise as adults, which could have far-reaching positive effects on human health and well-being." Although the positive effects of early-life exercise lasted for only one week, it is important to note that one week in the life of a mouse is the same as about nine months for humans. "Our results suggest that any positive effects of early-life exercise on adult exercise will need to be kept up if they are to be long-lasting." His team of researchers found, too, that all mice that had access to early exercise were lighter in weight than non-exercised mice. Garland explained that, in general, exercise will stimulate appetite sooner or later. However, it is possible that certain types of exercise, done for certain periods of time or at certain light levels, might not _ appetite much, if at all, at least in some individuals. "If we could understand what sorts of exercise these might be, then we might be able to tailor exercise recommendations in a way that would bring the benefits of exercise without increase in appetite, leading to a better chance of weight loss," he said. 
 Question: What is the article mainly about?
Example Output:
the positive effects of early- life exercise.