Cod sursa(job #893139)
Utilizator | Data | 26 februarie 2013 13:22:08 | |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.36 kb |
#include<cstdio>
using namespace std;
int i,j,n,phi[1000010],sol;
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d",&n);
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];
sol=1;
for(i=2;i<=n;i++) sol+=2*phi[i];
printf("%d\n",sol);
}