Cod sursa(job #757785)
Utilizator | Data | 13 iunie 2012 15:04:40 | |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.55 kb |
#include<stdio.h>
int a[1000000];
void ciuruire(int n)
{
int i,j;
for(i=2;i<=1000;++i)
if(a[i] == 0)
{
for(j=i*i;j<=n;j += i)
{
a[j] = i;
}
}
}
int fi(int n)
{
int f=n,c;
while(a[n])
{
c = a[n];
while(n%c == 0)
{
n /= c;
}
f = (f/c)*(c-1);
}
if( n > 1)
f = (f/n)*(n-1);
return f;
}
int main()
{
int n,s,i;
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%d",&n);
ciuruire(n);
s=1;
for(i=2;i<=n;i++)
s+=2*fi(i);
printf("%d",s);
return 0;
}