"\sum_{}**{}" is a continuation character, for example, 1+2+3 can be expressed as \sum_{i=1}**3i, that is, 1+2+3=\sum_{i=1} **3i=6, and 1+2+3+…+10 can be expressed as \sum_{i=1}**0i, 1+2+3+…+10=\sum_{i=1}** 0i=55; if \sum_{i=1}**(n)i=1540, then n=how much.
"\sum_{}**{}"是连加符，例如1+2+3可以表示成\sum_{i=1}**3i，即有1+2+3=\sum_{i=1}**3i=6，又有1+2+3+…+10可以表示为\sum_{i=1}**0i，1+2+3+…+10=\sum_{i=1}**0i=55；如果\sum_{i=1}**(n)i=1540，那么n=多少．
<result>55</result>