#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
const int mod = 998244353, N = 100001;

typedef pair<int, int> pi;

int main() {
	ios::sync_with_stdio(false), cin.tie(0);
	string s;
	cin >> s;
	int n = s.length(), a[n];
	a[0] = 0;
	for (int i = 1; i < n; ++i)
		a[i] = (a[i - 1] + (s[i] == 'L' ? 1 : 3)) % 4;
	int x = 2;
	while (a[x] == a[0])
		x += 2;
	int y = x + 2;
	while (y < n && a[y] == a[x])
		y += 2;
	bool is2 = true;
	for (int i = y; i < n; i += 2)
		if (a[i] != a[0])
			is2 = false;
	if (!is2) {
		x = 3;
		while (a[x] == a[1])
			x += 2;
		int b[n];
		for (int i = 0; i < n; ++i)
			b[i] = a[(x + i) % n];
		for (int i = 0; i < n; ++i)
			a[i] = b[i];
		// 10121012..30323032...
	}
	else {
		int x = 1, b[n];
		for (int i = 0; i < n; ++i)
			b[i] = a[(x + i) % n];
		for (int i = 0; i < n; ++i)
			a[i] = b[i];
		x = 2;
		while (a[x] == a[0])
			x += 2;
		int y = x + 2;
		while (y < n && a[y] == a[x])
			y += 2;
		for (int i = y; i < n; i += 2)
			if (a[i] != a[0])
				is2 = false;
		if (!is2) {
			x = 3;
			while (a[x] == a[1])
				x += 2;
			int b[n];
			for (int i = 0; i < n; ++i)
				b[i] = a[(x + i) % n];
			for (int i = 0; i < n; ++i)
				a[i] = b[i];
			// 10121012..30323032...
		}
		else {
			// t=2
			int cnt[4]{};
			for (int i = 0; i < n; ++i)
				++cnt[a[i]];
			int ans = max(cnt[0], cnt[2]) + max(cnt[1], cnt[3]);
			ans *= 2;
			if (cnt[0] == cnt[2] && cnt[1] == cnt[3]) {
				set<pi> s;
				int x = 0, y = 0;
				for (int i = 0; i < n; ++i) {
					if (a[i] == 0)
						++x;
					else if (a[i] == 1)
						++y;
					else if (a[i] == 2)
						--x;
					else
						--y;
					if (s.count({x, y})) {
						ans += 2;
						break;
					}
					s.insert({x, y});
				}
			}
			cout << ans << '\n';
			return 0;
		}
	}
	for (int i = 1; i < n; ++i)
		(a[i] += 4 - a[0]) %= 4;
	a[0] = 0;
	x = 0;
	vector<int> v[2];
	for (int i = 0; i < n; ++i) {
		if (i & 1) {
			if (!x)
				v[0].push_back(a[i] == a[n - 1] ? 1 : -1);
			else
				v[1].push_back(a[i] == a[n - 1] ? 1 : -1);
		}
		else if (a[i] != a[0])
			x = 1;
	}
	v[0].pop_back(), v[1].pop_back();
	reverse(all(v[1]));
	if (v[0].size() > v[1].size())
		swap(v[0], v[1]);
	int dp[N][2], inf = 0x3f3f3f3f;
	for (int j = 0; j <= v[1].size(); ++j)
		dp[j][0] = inf;
	dp[0][0] = 0;
	vector<int> pre[2];
	for (int i = 0; i < 2; ++i) {
		pre[i].push_back(0);
		for (int j = 0; j < v[i].size(); ++j)
			pre[i].push_back(pre[i].back() + v[i][j]);
	}
	for (int j = 0; j < v[1].size(); ++j) {
		int _j = j & 1, nxt = !_j;
		for (int i = 0; i <= v[0].size(); ++i)
			dp[i][nxt] = inf;
		for (int i = 0; i <= v[0].size(); ++i) {
			int dis = pre[0][i] + pre[1][j] + 1 + dp[i][_j];
			dp[i][nxt] = min(dp[i][nxt], dp[i][_j] + (dis + v[1][j] <= 0 ? 1 : 0));
			dp[i + 1][nxt] = min(dp[i + 1][nxt], dp[i][_j] + (dis + v[0][i] + v[1][j] <= 0 ? 1 - (dis + v[0][i] + v[1][j]) : (dis + v[0][i] + v[1][j] == 1 && dis == 1 ? 1 : 0)));
		}
	}
	int cnt[4]{};
	for (int i = 0; i < n; ++i)
		++cnt[a[i]];
	int dis = pre[0][v[0].size()] + pre[1][v[1].size()] + 1 + dp[v[0].size()][v[1].size() & 1];
	//cout << dis << '\n';
	int ans = 2 * max(cnt[0], cnt[2]) + cnt[1] + cnt[3] + dp[v[0].size()][v[1].size() & 1] + dis - 1;
	cout << ans << '\n';
	//cout << dp[v[0].size()][v[1].size() & 1] << '\n';
	//cout << 2 * max(cnt[0], cnt[2]) + cnt[1] + cnt[3] << '\n';
}