Cod sursa(job #2038319)
Utilizator | Data | 13 octombrie 2017 16:45:59 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.41 kb |
#include <fstream>
using namespace std;
ifstream cin ("fractii.in");
ofstream cout ("fractii.out");
const int MAX=1000000;
int v[MAX],n;
void euler(){
for (int i=1;i<=n;i++)
v[i]=i;
for(int i=2 ;i<=n;i++)
if(v[i]==i){
for(int j=i;j<=n;j+=i)
v[j]-=v[j]/i;
}
}
int main()
{
cin>>n;
euler();
long long s=-1;
for(int i=1;i<=n;i++)
s+=v[i]*2;
cout<<s;
return 0;
}