n(n+1)/2 + 1
求解过程如下：1个字符的子串（7个）:"s" "c" "i" "e" "n" "c" "e",2个字符（6个）："sc" "ci" "ie" "en" "nc" "ce".……6个字符（2个）：“scienc” “cience”7个字符（1个）:science 所以：共有7+6+5+4+3+2+1=28 ...