Cod sursa(job #361448)
Utilizator | Porcescu Alexandru TFifes | Data | 5 noiembrie 2009 05:22:57 |
---|---|---|---|
Problema | Fractii | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.47 kb |
#include<iostream>
#include<fstream>
#include<vector>
using namespace std;
int main ()
{
ifstream x("fractii.in");
ofstream y("fractii.out");
long n,i,j;
unsigned long long s=0;
unsigned int a;
x>>n;
vector<int>phi(n+1);
for(i=2;i<=n;i++)
phi[i]=phi[i-1];
for(i=2;i<=n;i++)
for(j=2*i;j<=n;j+=i)
phi[j]-=phi[i];
for(i=2;i<=n;i++)
s+=phi[i];
y<<s*2+1;
x.close();
y.close();
return 0;
}