Cod sursa(job #273012)
Utilizator | Data | 8 martie 2009 01:14:42 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.3 kb |
#include<stdio.h>
FILE *f=fopen("ciur.in","r"),*g=fopen("ciur.out","w");
bool a[2000005];
int main()
{
int n,i,j,nr=1;
fscanf(f,"%d",&n);
for(i=3;i*i<=n;i+=2)
if(!a[i])
{
for(j=i*i;j<=n;j+=i)
a[j]=1;
nr++;
}
for(;i<=n;i+=2)
nr+=!a[i];
fprintf(g,"%d\n",nr);
return 0;
}