Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Name | Position | Year | League\napps | League\ngoals | Total\napps | Total\ngoals | Notes |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Walter Langton | LB / CF | 1887–1905 | 45 | 28 | 48 | 48 | Doncaster's longest serving player\nAppearance stats don't include seasons 1887–1901 nor 1903–04 which are likely to put his total appearances over 400 |
| Tom Keetley | FW | 1923–1929 | 231 | 180 | 241 | 186 | Record all time goalscorer.\nMost goals in one game – 6 v Ashington in 1929 |
| Fred Emery | WH | 1924–1936 | 417 | 30 | 439 | 32 | Record league appearances\nManager of Doncaster 1936–1940 |
| Paddy McConnell | IF | 1925–1930 | 137 | 20 | 143 | 21 | The first current Doncaster player to represent his country at international level, Paddy played for Ireland |
| Syd Bycroft | DF | 1936–1951 | 333 | 2 | 355 | 2 | Including Wartime League matches, he played 501 games for Doncaster giving him the overall all-time record number of appearances.\nJoint manager of Doncaster January–June 1958 |
| Eddie Perry | CF | 1936–1938? | 98 | 44 | 102 | ? | Welsh international whilst at Doncaster |
| Clarrie Jordan | FW | 1945–1948 | 60 | 48 | 67 | 50 | Most Doncaster league goals in one season (42 in 1946/47) |
| Charlie Williams | DF | 1948–1959 | 158 | 1 | 174 | 1 | Famous comedian |
| Peter Doherty | IF | 1949–1953 | 103 | 55 | 109 | 58 | Ireland international player and manager of Northern Ireland whilst at Doncaster\nManager of Doncaster 1949–1958 (PM until 1953) |
| Len Graham | MF | 1949–1958 | 312 | 3 | 332 | 3 | Northern Ireland international whilst at Doncaster |
| Kit Lawlor | IF | 1950–1954 | 127 | 47 | 143 | 49 | Republic of Ireland international whilst at Doncaster |
| Harry Gregg | GK | 1952–1957 | 94 | 0 | 99 | 0 | Northern Ireland international whilst at Doncaster.\nHero of the Munich air disaster |
| Alick Jeffrey | FW | 1954–1956, 1963–1968 | 262 | 129 | 293 | 140 | Youngest Doncaster player (15 years 229 days v Fulham, 15 September 1954). |
| Colin Douglas | FW | 1981–1986, 1988–1993 | 404 | 53 | 444 | 62 | Record total appearances (not including the Wartime League games).\nForward in his first spell, fullback in his second |
| Brian Stock | MF | 2006–2012 | 193 | 18 | 216 | 23 | Welsh international whilst at Doncaster |
| Billy Sharp | FW | 2009–2012, 2014– | 92 | 44 | 96 | 45 | Record Transfer Fee Paid: £1,150,000 |
Question:
how many years did syd bycroft spend playing for doncaster?
Answer:
15