#include<fstream>
#include<algorithm>
#include<string>
using namespace std;

int a[10005],i,j,n,rs;
string s;

int main()
{
  ifstream cin("litere.in");
  ofstream cout("litere.out");

  cin>>n; getline(cin,s); getline(cin,s);

  for(i=0;i<n;++i)
   for(j=i-1;j>=0;--j)
   if(s[i]<s[j]) ++a[i];
   else if(s[i]==s[j]) a[i]+=a[j],j=-1;

  for(i=0;i<n;++i) rs+=a[i];

  cout<<rs<<'\n';

 return 0;
}