ll@n,z=0;
string@s;
rep(e,n)rep(d,e)rep(c,d)rep(b,c)rep(a,b)z+=s[a]==s[c]&&s[a]-s[b]&&s[a]-s[d]&&s[a]-s[e]&&s[b]-s[d]&&s[b]-s[e]&&s[d]-s[e];
wt(z);