#include<bits/stdc++.h>
using namespace std;
int n,num[30];char s[1000005];pair<int,int>val[1000005];
int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cin>>n>>(s+1);val[0]={0,0};
    for(int i=1;i<=n;i++)
    {
    	num[s[i]-'A']++;
    	val[i]={num[2]-num[0],num[1]-num[0]};
	}
	sort(val,val+n+1);
	int sum=1;long long ans=0;
	for(int i=1;i<=n;i++)
	{
		if(val[i]!=val[i-1])
		{
			ans+=1ll*sum*(sum-1)/2;
			sum=1;
		}
		else sum++;
	}
	ans+=1ll*sum*(sum-1)/2;
	cout<<ans;
	return 0;
}