#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
const int maxn = 1000000;
char str[maxn + 5];
vector<pair<int, int>> op;
#define mid (s.size() >> 1)
void print1(const vector<pair<int, int>>& s) {
	int sum = 0;
	for (int i = 0; i < mid; i++) sum += s[i].se;
	op.emplace_back(sum + 1, sum + s[mid].se);
	for (int i = 1; i <= mid; i++) {
		sum -= s[mid - i].se;
		op.emplace_back(sum + 1, sum + s[mid - i].se + s[mid + i].se);
	}
}
void print2(const vector<pair<int, int>>& s) {
	int l, r;
	for (l = mid; !s[l].fi; l--) ;
	for (r = mid; !s[r].fi; r++) ;
	int sum = 0;
	for (int i = 0; i < l; i++) sum += s[i].se;
	op.emplace_back(sum + 1, sum + s[l].se);
	for (int i = 1; i < r - mid; i++) {
		sum -= s[l - i].se;
		op.emplace_back(sum + 1, sum + s[l - i].se + s[l + i].se);
	}
	vector<pair<int, int>> lft(s.begin(), s.begin() + l - r + mid);
	lft.emplace_back(1, s[l - r + mid].se + s[l + r - mid].se);
	lft.insert(lft.end(), s.begin() + l + r - mid + 1, s.end());
	print1(lft);
}
bool ok[maxn + 5];
int main() {
	int n;
	scanf("%d%s", &n, str + 1);
	vector<pair<int, int>> s;
	for (int l = 1, r; l <= n; l = r + 1) {
		for (r = l; r < n && str[r + 1] == str[l]; r++) ;
		s.emplace_back(r > l, r - l + 1);
	}
	if (s.size() % 2 == 1) {
		if (s[mid].fi) print1(s);
		else {
			int mx = 0, nw = 0;
			for (const auto& x : s) mx = max(mx, nw = x.fi ? nw + 1 : 0);
			if (mx < mid) print2(s);
			else return printf("-1"), 0;
		}
	} else {
		int mx = 0, nw = 0;
		for (int i = s.size() - 1; ~i; i--) {
			mx = max(mx, nw = s[i].fi ? nw + 1 : 0);
			if (i & 1) ok[i] = mx < (s.size() - i) / 2 || s[(s.size() + i) / 2].fi;
		}
		mx = nw = 0;
		for (int i = 0; i < s.size(); i++) {
			mx = max(mx, nw = s[i].fi ? nw + 1 : 0);
			if (i & 1 ^ 1 && ok[i + 1] && (mx < i / 2 || s[i / 2].fi)) {
				vector<pair<int, int>> s1(s.begin(), s.begin() + i + 1), s2(s.begin() + i + 1, s.end());
				s[i / 2].fi ? print1(s1) : print2(s1);
				s[(s.size() + i) / 2].fi ? print1(s2) : print2(s2);
				goto ed;
			} 
		}
		return printf("-1"), 0;
	}
	ed: printf("%zu\n", op.size());
	for (const auto& p : op) printf("%d %d\n", p.fi, p.se);
}