Hello, everyone I was trying to solve this from VK Cup Qualification round, after trying for a hour I gave up and read editorial, but it was not clearly explained, Plz can anybody explain in more detail why we are taking factors it to me as it will be very helpful to me. Thank you.

I was reading ACM-ICPC rules, there I read that "Team should not participate in more than 5 regionals". What does it mean ? Is it for same year or entire college life ?

I was solving a problem "Sorting a three value sequence" USACO training gateway. I managed to solve the problem on my own. But in analysis section I found a solution given below, I was unable to understand whats the use of 2*(max(s12, s21)- min(s12, s21). plz explain me I am a newbie ?

#include <fstream>

using namespace std;

int min (int a, int b) { return a < b ? a : b; }
int max (int a, int b) { return a > b ? a : b; }

int main () {
    int s[1024];
    int n;
    int sc[4] = {0};
    
    ifstream fin("sort3.in");
    ofstream fout("sort3.out");
    fin>>n;
    for (int i = 0; i < n; i++) {
        fin>>s[i];
        sc[s[i]]++;
    }
    int s12 = 0, s13 = 0, s21 = 0, s31 = 0, s23 = 0, s32 = 0;
    for (int i = 0; i < sc[1]; i++){
        if (s[i] == 2) s12++;
        if (s[i] == 3) s13++;
    }
    
    for (int i = sc[1]; i < sc[1]+sc[2]; i++){
        if (s[i] == 1) s21++;
        if (s[i] == 3) s23++;
    }
    
    for (int i = sc[1]+sc[2]; i < sc[1]+sc[2]+sc[3]; i++){
        if (s[i] == 1) s31++;
        if (s[i] == 2) s32++;
    }
    
    fout<<min(s12, s21)+min(s13, s31)+min(s23, s32) +
					2*(max(s12, s21) - min(s12, s21))<<endl;
    return 0;
}

Hello everyone, I need help in solving this problem.