Cod sursa(job #288413)
Utilizator | Puia Tudor yotherocker | Data | 25 martie 2009 19:33:29 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.47 kb |
#include<fstream.h>
#include<math.h>
unsigned long i=3,n,ciur=1;
unsigned long PRIM(unsigned long);
main()
{
ifstream In("ciur.in");
ofstream Out("ciur.out");
In>>n;
In.close();
for(;i<=n;i+=2)
{
if(i>5 && (i%3==0 || i%5==0)) continue;
if(PRIM(i)) ciur++;
}
Out<<ciur<<'\n';
Out.close();
return 0;
}
unsigned long PRIM(unsigned long x)
{
short ok=1;
for(unsigned long d=3;d<=sqrt(x);d+=2) if(x%d==0) {ok=0;break;}
return ok;
}