#include <bits/stdc++.h>

int ri() {
	int n;
	scanf("%d", &n);
	return n;
}

// 3乗で通したお詫びにO(NlogN)で通します
// 参考 : https://twitter.com/SayakaAmemiya/status/1249515024541859842

template<int mod, int proot> struct NTT {
	int get_mod() { return mod; }
	int pow(int a, int b) {
	int res = 1;
		for (; b; b >>= 1) {
			if (b & 1) res = (int64_t) res * a % mod;
			a = (int64_t) a * a % mod;
		}
		return res;
	}
	int inv(int i) { return pow(i, mod - 2); }
	void ntt(std::vector<int> &a, bool inverse) {
		int n = a.size();
		assert((n & -n) == n);
		int h = pow(proot, (mod - 1) / n);
		if (inverse) h = inv(h);
		
		for (int i = 0, j = 1; j < n - 1; j++) {
			for (int k = n >> 1; k > (i ^= k); k >>= 1);
			if (j < i) std::swap(a[i], a[j]);
		}
		for (int i = 1; i < n; i <<= 1) {
			int base = pow(h, n / i / 2);
			int w = 1;
			
			std::vector<int> ws(i);
			for (int j = 0; j < i; j++) ws[j] = w, w = (int64_t) w * base % mod;
			
			for (int j = 0; j < n; j += i << 1) {
				for (int k = 0; k < i; k++) {
					int u = a[k + j];
					int d = (int64_t) a[k + j + i] * ws[k] % mod;
					a[k + j] = u + d >= mod ? u + d - mod : u + d;
					a[k + j + i] = d > u ? u + mod - d : u - d;
				}
			}
		}
		if (inverse) {
			int ninv = inv(a.size());
			for (auto &i : a) i = (int64_t) i * ninv % mod;
		}
	}
};

int main() {
	int n = ri();
	int back[3] = { 0 };
	int forward[3] = { 0 };
	std::vector<int> a(n);
	{
		char tmp[4096];
		scanf("%s", tmp);
		for (int i = 0; i < n; i++) {
			a[i] = tmp[i] == 'R' ? 0 : tmp[i] == 'G' ? 1 : 2;
			back[a[i]]++;
		}
	}
	
	int64_t res = 0;
	// j - i != k - jを無視したの
	for (int j = 0; j < n; j++) {
		back[a[j]]--;
		res += forward[(a[j] + 1) % 3] * back[(a[j] + 2) % 3];
		res += forward[(a[j] + 2) % 3] * back[(a[j] + 1) % 3];
		forward[a[j]]++;
	}
	// j - i == k - jで相異なるものを引く
	int n2 = 1;
	for (; n2 < n + n - 1; n2 <<= 1);
	NTT<40961, 3> ntt;
	std::vector<int> count[3];
	for (auto &i : count) i.resize(n2);
	for (int i = 0; i < n; i++) count[a[i]][i]++;
	for (auto &i : count) ntt.ntt(i, false);
	
	std::vector<int> conved[3]; // conved count[i], count[(i + 1) % 3]
	for (int i = 0; i < 3; i++) {
		auto &cur = conved[i];
		cur.resize(n2);
		for (int j = 0; j < n2; j++) cur[j] = (int64_t) count[i][j] * count[(i + 1) % 3][j] % 40961;
		ntt.ntt(cur, true);
	}
	for (int j = 0; j < n; j++) res -= conved[(a[j] + 1) % 3][j + j];
	
	printf("%" PRId64 "\n", res);
	
	return 0;
}
