Section $1$:

Problem

Input: $,$ An array $A[0..n-1]($of comparable elements$)$

Output: $,$ The total number of pairs $(i,j)$ such that $A[i]>A[j]s[x]xss[0$dotssL$-1]r[0$dotsrL$-1]s>$rrsAAp$=0$dotsrL$-1,s[p]=r[p]ks[k]>r[k]AAp=0$dotsk$-1s[p]=r[p]rL$ and AAp$=0$dotsrL$-1,s[p]=r[p]$ i and $A[i]>A[j].$

$In$ this problem, the input can $bean$ array $of$ integers $oran$ array $of$ strings.

$(1\mathrm{.}1)$ Comparison for strings

$We$ use the lexicographical order $to$ compare strings.

Let $s[x]$ denote the $x-th$ letter $of$ the string $s.$

Given two strings $s[0$dotssL$-1]$ and $r[0$dotsrL$-1],$

$s>r$ holds $if$

$ris$ a prefix $ofs(i.e.,rL$ and AAp$=0$dotsrL$-1,s[p]=r[p])$

there exists a position $k$ such that $s[k]>r[k]$ and AAp$=0$dotsk$-1s[p]=r[p]$

Examples:

charge $>$ balance

balance $>$ bal

$bbbbbb>$ bbbbba

$(1\mathrm{.}2)$ Examples for the problem