Cod sursa(job #2029116)
Utilizator | tudor P ptudor | Data | 29 septembrie 2017 13:03:12 |
---|---|---|---|
Problema | Fractii | Scor | 0 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.65 kb |
#include <iostream>
#include <fstream>
using namespace std;
long long n;
bool v[1000000];
long long ciur()
{
int i,j;
for (i=4;i<=n;i=i+2)
v[i]=1;
long long n2=n*n;
for (i=3;i*i<=n;i=i+2)
{
if (v[i]==0)
{
for (j=i*i;j<=n;j=j+i*2)
{
v[j]=1;
}
}
}
for (i=2;i<=n;i++)
{
if (v[i]==0)
n2=n2-((n/i)*(n/i))+n/i;
}
return n2-n+1;
}
int main()
{
ifstream in("fractii.in");
ofstream out("fractii.out");
in>>n;
out<<ciur();
out.close();
in.close();
return 0;
}