Cod sursa(job #398690)
Utilizator | Data | 19 februarie 2010 10:29:44 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 30 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.49 kb |
//
#include<stdio.h>
FILE *f=fopen("ciur.in","r"), *g=fopen("ciur.out","w");
int v[2000001];
long k,i,j,pozp,p,n,ctr;
int main()
{
fscanf(f,"%ld", &n);
for(i=2;i<=n;i++)
v[i]=i;
p=2;
pozp=2;
while(ctr<n)
{
for(j=p*p;j<=n;j++)
if(v[j]%p==0)
v[j]=0;
pozp++;
while(v[pozp]==0)
pozp++;
p=v[pozp];
ctr=p*p;
}
k=0;
for(i=1;i<=n;i++)
if(v[i]!=0)
k++;
fprintf(g,"%ld",k);
fclose(f);
fclose(g);
return 0;
}