Cod sursa(job #228083)
Utilizator | Data | 6 decembrie 2008 13:29:48 | |
---|---|---|---|
Problema | Fractii | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.71 kb |
#include<stdio.h>
#define nmax 1000001
long long a[nmax];
int main()
{
long long unsigned n,i,j,sol=0;
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%llu",&n);
for(i=2;i<=n/2;++i)
{
if (a[i]==0)
{
for(j=2*i;j<=n;j+=i)
if (a[j]==0)
a[j] = j - j/i;
else
a[j] -= a[j]/i;
sol+=i-1;
}
else
sol+=a[i];
}
for(i=n/2+1;i<=n;++i)
if (a[i]==0)
sol+=i-1;
else
sol+=a[i];
printf("%llu",2*sol+1);
return 0;
}