Cod sursa(job #3201580)
Utilizator | Sasha Costea Sasha_12454 | Data | 9 februarie 2024 08:40:04 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.64 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
const int NMAX=1000005;
int n;
int phi[NMAX];
int precalc()
{
long long res=0;
for(int i=1; i<=n; i++)
phi[i]=i;
for(int i=2; i<=n; i++)
{
if(phi[i]==i)
{
for(int j=i; j<=n; j+=i)
phi[j]-=phi[j]/i;
}
}
//for(int i=1;i<=n;i++)
//cout<<phi[i]<<" ";
for(int i=2; i<=n; i++)
{
//cout<<res<<" ";
res+=phi[i];
}
return (1LL*res*2+1);
}
int main()
{
in>>n;
out<<precalc();
return 0;
}