char s[],a[1030][11];r,t,i,n;c(a,b){r=strcmp(a,b);}main(l){for(n=read(0,s)-1;i--?a[t][i]=s[t&1<<i?l++:--r]:!(i=r=n,l=t++>>n););for(qsort(a,t,11,c);t;l+=!!c(a[t],a[t--]));printf("%d",l-2);}