Cod sursa(job #878051)
Utilizator | Ion Sebastian IonSebastian | Data | 13 februarie 2013 20:36:01 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.49 kb |
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
long long e[1000001];
int main()
{
int i,n,j;
long long x=0;
in>>n;
for(i=2;i<=n;i++){
e[i]=i;
}
for(i=2;i<=n;i++){
if(e[i]==i){
for(j=i;j<=n;j+=i){
e[j]=e[j]/i*(i-1);
}
}
}
for(i=2;i<=n;i++){
x+=e[i];
}
out<<2*x+1;
in.close();
out.close();
return 0;
}