#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;

int n, m, pre[N], nxt[N], sum[N];
vector< pair<int, int> > p;

int get(int x) {
    int tx = x, s = 0;
    for (; x; x -= x & -x) s += sum[x];
    for (x = tx; x <= n; x += x & -x) --sum[x];
    return s;
}

set<int> S;
vector< pair<int, int> > res;

void del(int l, int r) {
    l = p[l].first, r = p[r].second;
    vector<int> arr;
    for (auto it = S.lower_bound(l); it != S.end() && *it <= r; ++it) {
        arr.push_back(*it);
    }
    for (auto x : arr) S.erase(x);
    while (arr.size() >= 5 || arr.size() == 3) {
        res.push_back({get(arr.end()[-3]), 3});
        get(arr.end()[-2]), get(arr.end()[-1]);
        arr.erase(arr.end() - 3, arr.end());
    }
    while (arr.size() >= 2) {
        res.push_back({get(arr.end()[-2]), 2});
        get(arr.end()[-1]);
        arr.erase(arr.end() - 2, arr.end());
    }
}

void solve(int l, int r) {
    if (p[(l + r) / 2].first != p[(l + r) / 2].second) {
        for (int tl = (l + r) / 2, tr = (l + r) / 2; tl >= l && tr <= r; --tl, ++tr) {
            del(tl, tr);
        }
    } else {
        int fi = (l + r) / 2, se = (l + r) / 2;
        while (p[fi].first == p[fi].second) --fi;
        while (p[se].first == p[se].second) ++se;
        vector<int> z;
        for (int i = 1; i <= se - (l + r) / 2; ++i) {
            del(fi - i + 1, fi + i - 1);
        }
        for (int i = l; i <= fi - (se - (l + r) / 2); ++i) z.push_back(i);
        for (int i = fi + (se - (l + r) / 2) + 1; i <= r; ++i) z.push_back(i);
        for (int tl = z.size() / 2, tr = z.size() / 2; tl >= 0 && tr < (int)z.size(); --tl, ++tr) {
            del(z[tl], z[tr]);
        }
    }
}

signed main() {
    scanf("%d", &n);
    string str; cin >> str;
    int lst = 1;
    for (int i = 0; i <= n; ++i) {
        if (i == n || (i != 0 && str[i] != str[i - 1])) p.push_back({lst, i}), lst = i + 1;
    }
    m = p.size();
    for (int i = 0, len = 0; i < m; ++i) {
        if (p[i].first == p[i].second) ++len;
        else len = 0;
        pre[i] = len;
        if (i) pre[i] = max(pre[i], pre[i - 1]);
    }
    for (int i = m - 1, len = 0; ~i; --i) {
        if (p[i].first == p[i].second) ++len;
        else len = 0;
        nxt[i] = len;
        if (i != m - 1) nxt[i] = max(nxt[i], nxt[i + 1]);
    }
    for (int i = 1; i <= n; ++i) {
        ++sum[i];
        if (i + (i & -i) <= n) sum[i + (i & -i)] += sum[i];
        S.insert(i);
    }
    if (m & 1) {
        if (p[m / 2].first != p[m / 2].second || pre[m - 1] < m / 2) {
            solve(0, m - 1);
        }
    } else {
        for (int i = 0; i < m; i += 2) {
            if ((p[i / 2].first != p[i / 2].second || pre[i] < i / 2) && (p[(i + m) / 2].first != p[(i + m) / 2].second || pre[i + 1] < (m - i - 2) / 2)) {
                solve(0, i), solve(i + 1, m - 1);
                break;
            }
        }
    }
    if (res.empty()) return 0 & puts("-1");
    printf("%d\n", (int)res.size());
    for (auto [x, y] : res) printf("%d %d\n", x, y);
    return 0;
}