Cod sursa(job #523597)
Utilizator | Data | 18 ianuarie 2011 17:08:59 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 10 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.41 kb |
#include<stdio.h>
long long n,prim[2000001],nr;
int primes(long long n)
{
int i,j,nr=1;
for(i=2;i<=n;++i) prim[i]=1;
for(i=4;i<=n;i+=2) {prim[i]=0; nr++;}
for(i=3; i*i<=n; i+=2)
if(prim[i])
for(j=i*i;j<=n;j+=i) {prim[j]=0; nr++;}
return n-nr;
}
int main()
{
freopen("ciur.in","rt",stdin);
freopen("ciur.out","wt",stdout);
scanf("%lld",&n);
nr=primes(n);
printf("%lld",nr);
return 0;
}