题解 | #涂颜料#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {

    static int n, q;
    static char[] rgb = new char[] {'R', 'G', 'B'};
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        n = in.nextInt();
        q = in.nextInt();
        int[] grid = new int[n];
        for (int k = 0; k < q; k++) {
            int l = in.nextInt();
            int r = in.nextInt();
            //差分数组
            grid[l - 1]++;
            if (r < n) {
                grid[r]--;
            }
        }
        for (int i = 0; i < n; i++) {
            if (i == 0) {
                grid[i] = grid[0];
            } else {
                //差分还原
                grid[i] += grid[i - 1];
            }
            if (grid[i] == 0) {
                System.out.print("O");
            } else {
                System.out.print(rgb[(grid[i] - 1) % 3]);
            }

        }

    }

}