#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <utility>
#include <cmath>
#include <tuple>
#include <queue>
#include <bitset>
#include <set>
#include <map>
#include <list>

using ll = long long;
using ld = long double;
using namespace std;
const int INF = 1e9+100;
const ll INF64 = 7e18l;
const int mod = 1000000007;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define ALL(a) (a).begin(), (a).end()
#define FIN ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);


int main(){
    FIN;
    ll n;  cin >> n;
    vector<char> rgb(n);
    for(int i=0;i<n;i++) cin >> rgb[i];

    ll ans = 0;
    for(int i=0;i<n-2;i++){
        for(int j=i+1;j<n-1;j++){
            for(int k=j+1;k<n;k++){
                if(rgb[i]!=rgb[j] and rgb[j]!=rgb[k] and rgb[k]!=rgb[i] and (i+k)!=(2*j))
                    ans ++;
            }
        }
    }

    cout << ans << endl;
    return 0;
}
