Cod sursa(job #361449)
Utilizator | Data | 5 noiembrie 2009 05:41:48 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.45 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;
x>>n;
vector<int>phi(n+1);
for(i=1;i<=n;++i)
phi[i]=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;
}