Cod sursa(job #1205008)
Utilizator | Pavlov Ion pavlov.ion | Data | 4 iulie 2014 17:42:40 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.47 kb |
#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int N,phi[1000001];
long long s;
int main(){
cin>>N;
//daca i e prim phi[i]=phi=i-1
for (int i = 1; i <= N; ++i)
phi[i] = i-1;
for (int i = 2; i <= N; ++i)
for (int j = 2*i; j <= N; j += i)
phi[j] -= phi[i];
for(int i=2;i<=N;i++)
s+=phi[i];
cout<<2*s+1;
return 0;
}