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Cod sursa(job #6075)
#include<fstream.h>
#define input "fractii.in"
#define output "fractii.out"
char a[10000];
long tot(long p)
{
int i=2;
long t=p;
while(i<=p)
{
if(a[i]!='1'&&p%i==0)
{
t=t*(i-1)/i;
while(p%i==0)
p=p/i;
if(a[p]!='1')
{
t=t*(p-1)/p;
break;
}
}
i++;
}
return t;
}
int main()
{
long n,p,q;
unsigned long long nr,h;
ifstream fin(input);
ofstream fout(output);
fin>>n;
h=0;
a[1]='1';
nr=1;
for(p=2;p<=n;p++)
{
if(a[p]!='1')
{
nr+=2*(p-1);
for(q=p+p;q<=n;q=q+p)
a[q]='1';
}
else
nr+=2*tot(p);
if(nr>1000000000)
{
h=h+(nr/1000000000);
nr=nr%1000000000;
}
}
fout<<h<<nr<<"\n";
fin.close();
fout.close();
return 0;
}