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Cod sursa(job #592266)
#include <fstream>
#include <algorithm>
using namespace std;
int N, M;
int phi[1000002];
long long total;
int main()
{
ifstream fin("mins.in");
ofstream fout("mins.out");
fin >> N >> M;
--N, --M;
if (N < M) swap(N, M);
for (int i = 1; i <= N; ++i)
phi[i] = i;
for (int i = 2; i <= N; ++i)
if (phi[i] == i)
for (int j = i; j <= N; j += i)
phi[j] -= phi[j] / i;
for (int i = 1; i <= N; ++i)
total += phi[i];
total *= 2, --total;
for (int i = M + 1; i <= N; ++i)
total -= phi[i];
fout << total;
fin.close();
fout.close();
}