Determine doc math score by the max expr scores.
Determine doc math score by the max expr scores.

Not by sum of expression scores.

t-k-/the-day-after-tomorrow,approach0/search-engine,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,t-k-/the-day-after-tomorrow,approach0/search-engine,yzhan018/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,approach0/search-engine,approach0/search-engine,t-k-/the-day-after-tomorrow,yzhan018/the-day-after-tomorrow,t-k-/the-day-after-tomorrow