Cod sursa(job #28383)
Utilizator | Bogdan P. dodgerblue | Data | 7 martie 2007 19:32:29 |
---|---|---|---|
Problema | Fractii | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.52 kb |
#include<fstream.h>
int e[1000000],n;
long long int s=1,p;
int main()
{
int i,j;
ifstream f("fractii.in");
f>>n;
f.close();
for(i=1;i<=n;i++)
e[i]=1;
for(i=2;i<=n/2;i++)
if(e[i]==1)
for(j=2;j*i<=n;j++)
e[i*j]=0;
for(i=2;i<=n;i++)
{
if(e[i]==0)
{
p=i;
for(j=2;j<i;j++)
if(e[j]==1 && i%j==0)
{
p*=j-1;
p/=j;
}
}
else
p=i-1;
s+=p*2;
}
ofstream g("fractii.out");
g<<s<<"\n";
g.close();
return 0;
}