#include<bits/stdc++.h>
#define ll long long
#define il inline
#define pn putchar('\n')
#define maxint 2147483647
#define min(x,y) (x<y?x:y)
#define max(x,y) (x>y?x:y)
#define int ll
using namespace std;
int n,ca,cb,cc,ans;
string s;
unordered_map<int,unordered_map<int,unordered_map<int,int>>>f;
signed main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt","r",stdin);
    #endif
    scanf("%lld",&n);
    cin>>s;
    f[0][0][0]=1;
    for(int i=0;i<n;i++)
    {
        if(s[i]=='A')
            ca++;
        if(s[i]=='B')
            cb++;
        if(s[i]=='C')
            cc++;
        while(ca&&cb&&cc)
            ca--,cb--,cc--;
        ans+=f[ca][cb][cc];
        f[ca][cb][cc]++;
    }
    printf("%lld",ans);
    return 0;
}