Cod sursa(job #349048)
Utilizator | Panaete Adrian proflaurian | Data | 17 septembrie 2009 20:28:07 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.51 kb |
#include<stdio.h>
int n,i,j,p,E[1000001];
void read(),solve();
int main()
{
read();
solve();
return 0;
}
void read()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d",&n);
}
void solve()
{
unsigned long long sol=1;
for(i=2;i<=n;i++)
{
if(!E[i])
{
E[i]=i-1;
for(j=i*i;j<=n;j+=i)E[j]=i;
}
else
{
p=E[i];j=i;
E[i]=p-1;j/=p;
while(j%p==0){E[i]*=p;j/=p;}
if(j>1)E[i]*=E[j];
}
sol+=2*E[i];
}
printf("%llu\n",sol);
}