Cod sursa(job #2577127)
Utilizator | Octavian Neculau 1chiriac | Data | 8 martie 2020 14:26:39 |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.43 kb |
#include <bits/stdc++.h>
using namespace std;
int n,v[1000006];long long ans;
int main () {
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d", &n);
ans=1;
for(int i=1;i<=n;++i)
v[i]=i;
for(int i=2;i<=n;++i)
if(v[i]==i) {
for(int j=2;j*i<=n;++j)
v[i*j]=v[i*j]/i*(i-1);
}
for(int i=2;i<=n;++i)
if(v[i]==i)
ans=ans+(v[i]-1)*2;
else
ans=ans+2*v[i];
printf("%lld", ans);
return 0;
}