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Cod sursa(job #607885)
#include<fstream>
using namespace std;
short c[1000002],i,j,n,v[1000000],u,k=1;
long long rez;
void ciur(int n)
{
for(int i=2;i<=n/2;i++)
if(!c[i])
{
for(j=2;j<=n/i;j++)
c[i*j]=1;
}
for(i=2;i<=n;i++) if(!c[i]) v[++u]=i;
}
int main()
{
ifstream f("fractii.in");ofstream g("fractii.out");
f>>n;
ciur(n);
for(i=2;i<=n;i++)
for(j=2;j<=n;j++)
if(i%j && j%i)
{
for(k=1; v[k] && v[k]<=j &&(!j%v[k] && !i%v[k]); k++);
if(v[k]>=j ) rez++;
}
g<<rez+n+n-1<<" ";
f.close();g.close();
return 0;}