Cod sursa(job #3348723)

Utilizator Radu_BicliBiclineru Radu Radu_Bicli Data 23 martie 2026 18:27:20
Problema Pairs Scor 50
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 0.98 kb
#include <bits/stdc++.h>

using namespace std;

#define USE_STD_IO 0
#if USE_STD_IO
    #define fin cin
    #define fout cout
#else
    ifstream fin("pairs.in");
    ofstream fout("pairs.out");
#endif // USE_STD_IO

const int MAX = 1000002;
int n, i, j, cmmdc[MAX + 2], a[100002];
int fr[MAX + 2];

static inline int Cmmdc(int a, int b) {
    if(0 == a) return b;
    if(0 == b) return a;
    int rest;
    do {
        rest = a % b;
        a = b;
        b = rest;
    }
    while(0 != b);
    return a;
}

int main() {
    if(USE_STD_IO) ios_base::sync_with_stdio(false);
    fin.tie(NULL);
    fout.tie(NULL);

    fin >> n;
    for(i = 1; i <= n; i++) {
        fin >> a[i];
        fr[a[i]]++;
    }
    for(i = MAX; i >= 1; i--) {
        int cm = 0;
        for(j = i; j <= MAX; j += i) cm += fr[j];
        cmmdc[i] = cm * (cm + 1) / 2;
        for(j = 2 * i; j <= MAX; j += i) cmmdc[i] -= cmmdc[j];
    }
    fout << cmmdc[1];

    return 0;
}