Cod sursa(job #350988)
Utilizator | Ioana Radu iora | Data | 26 septembrie 2009 14:13:54 |
---|---|---|---|
Problema | Fractii | Scor | 10 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.4 kb |
#include<cstdio>
#define N 1000001
long long s=0,e[N];
int i,n;
long long era(int n)
{
int i,j;
for(i=2;i<=n;++i)
e[i]=i;
for(i=2;i<=n;++i)
if(e[i]==i)
for(j=i;j<=n;j=j+i)
e[j]=e[j]/i*(i-1);
return e[n];
}
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d",&n);
for(i=2;i<=n;++i)
s+=era(i);
printf("%lld",2*s+1);
return 0;
}