algorithm - A simple code to detect the permutation sign -

supposed have array of integers:

1 2 5 3 7 6 

what simple enough algorithm determines if or odd permutation of numbers in sorted fashion (i.e. 1 2 3 5 6 7)? performance not terribly important here; i'd rather have simple code.

simple code(assume n numbers stored in array a):

int f() {     int cnt=0;     for(int i=0;i<n;i++)         for(int j=i+1;j<n;j++)             if (a[i]>a[j]) cnt++;     return cnt%2; } 

if f() returns 0, permutation , returns 1, odd.