Cod sursa(job #2298275)
Utilizator | Data | 7 decembrie 2018 21:38:22 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.42 kb |
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
long long n, phi[1000100], S;
void generarePhi(long long n)
{
for(int i=1; i<=n; i++) phi[i] = i-1;
for(int i=2; i<=n; i++)
for(int j=i*2; j<=n; j+=i) phi[j]-=phi[i];
}
int main()
{
f >> n;
generarePhi(n);
for(int i=2; i<=n; i++) S+=phi[i];
g << 2*S + 1 << '\n';
return 0;
}