Cod sursa(job #228878)
Utilizator | voloc cristina loredana necropriest | Data | 8 decembrie 2008 17:17:14 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.44 kb |
#include<stdio.h>
const int N=1000000;
int e[N];
void euler()
{
for(int j=1;j<N;++j)
e[j]=j;
for(int i=2;i<N;++i)
if(e[i]==i)
for(int j=i;j<N;j+=i)
e[j]=e[j]/i*(i-1);
}
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
int n;
scanf("%d",&n);
euler();
int s=0;
for(int i=2;i<=n;++i)
s+=e[i];
printf("%d\n",1+2*s);
fclose(stdin);
fclose(stdout);
return 0;
}