#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;

    string s;
    cin >> s;

    vector dp(n, vector<int>(n));

    for (int l = n - 1; l >= 0; --l) {
        for (int r = l + 1; r < n; ++r) {
            if (r <= l + 2 && s[l] == s[r] && s[l] == s[l + r >> 1]) {
                dp[l][r] = -1;
            } else {
                for (int mid = l + 1, cnt = 0; mid + 1 < r && ++cnt <= 100; ++mid) {
                    if (dp[l][mid] && dp[mid + 1][r]) {
                        dp[l][r] = mid;
                        break;
                    }
                }
                if (!dp[l][r] && s[l] == s[r]) {
                    for (int mid = l + 1, cnt = 0; mid < r && cnt < 100; ++mid) {
                        if (s[mid] == s[l] && (l + 1 > mid - 1 ? true : dp[l + 1][mid - 1]) && (mid + 1 > r - 1 ? true : dp[mid + 1][r - 1])) {
                            dp[l][r] = ~mid;
                            break;
                        }
                        cnt += s[mid] == s[l];
                    }
                    if (dp[l + 1][r - 1]) {
                        dp[l][r] = r;
                    }
                }
            }
        }
    }

    if (!dp[0][n - 1]) {
        cout << "-1\n";
        return 0;
    }

    vector<pair<int, int>> ans;

    auto dfs = [&](auto dfs, int l, int r, int del) -> int {
        if (l > r) {
            return 0;
        }
        if (l + 2 >= r) {
            ans.push_back({l - del, r - l + 1});
            return r - l + 1;
        }
        if (dp[l][r] >= 0) {
            int mid = dp[l][r];
            if (mid < r) {
                del += dfs(dfs, l, mid, del);
                dfs(dfs, mid + 1, r, del);
            } else {
                dfs(dfs, l + 1, r - 1, del);
                ans.push_back({l - del, 2});
            }
        } else {
            int mid = ~dp[l][r];
            int d = del;
            del += dfs(dfs, l + 1, mid - 1, del);
            del += dfs(dfs, mid + 1, r - 1, del);
            ans.push_back({l - d, 3});
        }
        return r - l + 1;
    };

    dfs(dfs, 0, n - 1, 0);

    cout << size(ans) << '\n';

    for (auto [l, r] : ans) {
        cout << l + 1 << " " << r << '\n';
    }

    return 0;
}