# include <stdio.h>
int k=0,i,n,j,l,p;
char a[1000],aux,min;
int main ()
{
freopen ("litere.in","r",stdin);
freopen ("litere.out","w",stdout);


scanf ("%ld",&n);
scanf ("%c");
for (i=0;i<=n;i++)
scanf ("%c",&a[i]);
for (i=0;i<n-1;i++)
{p=i;
min=a[i];
for (j=i+1;j<n;j++)
if (a[j]<min)
{
p=j;
min=a[j];
}
aux=a[p];
for (l=p;l>i;l--)
a[l]=a[l-1];
a[i]=aux;
k=k+(p-i);
}
printf ("%ld",k);
fclose (stdout);
return 0;
}