Given the task definition and input, reply with output. In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Passage: During those two years Warner also played two games against John Heisman, another future coaching legend. Heisman was the head coach at Auburn University, and they faced each other in the 1895 and 1896 games of the "Deep South's Oldest Rivalry," an annual confrontation which has continued to the present day. In 1895, the Auburn Tigers defeated the Bulldogs 126. The Auburn team was led by quarterback Reynolds "Tick" Tichenor, known for his punt returns. Tichenor had executed the first "hidden-ball trick" in an earlier Auburn game against Vanderbilt, and used it again against Georgia. The next year, Tichenor faced Georgia's Richard Von Albade Gammon, a star quarterback in his first year under Warner. Both quarterbacks played well and, unlike the previous year, Warner's team won 166. The second touchdown came right after the first onside kick in the South.
Link Information: Heisman coached football at Auburn from 1895 to 1899. Question: How long was Heisman head coach at Auburn?
Answer: 4