Cod sursa(job #2364311)

Utilizator herbiculusMihai Panduru herbiculus Data 3 martie 2019 23:29:05
Problema Fractii Scor 100
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 0.35 kb
Raporteaza aceasta sursa 
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int fr[1000001],n,i,j;
long long num;
int main()
{
    f>>n;
    for (i=2;i<=n;++i)
        fr[i]=i-1;
    for (i=2;i<=n/2;++i)
        for (j=2*i;j<=n;j+=i)
            fr[j]-=fr[i];
    for (i=2;i<=n;++i)
        num+=fr[i];
    g<<num*2+1;
}