Cod sursa(job #885040)
Utilizator | Mihai Ion linerunner | Data | 21 februarie 2013 16:25:34 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.45 kb |
#include<fstream>
#include<iostream>
using namespace std;
int n;
int phi[1000000];
long long ct;
int main()
{
int i, j;
ifstream f("fractii.in");
ofstream g("fractii.out");
f>>n;
for(i=2; i<=n; i++)
phi[i]=i-1;
for(i=2; i<=n; i++)
for(j=2*i; j<=n; j=j+i)
phi[j]-=phi[i];
for(i=2; i<=n; i++)
ct+=phi[i];
ct=2*ct+1;
g<<ct;
f.close();
g.close();
return 0;
}