Cod sursa(job #565689)
Utilizator | Vlad Schnakovszki shnako | Data | 28 martie 2011 10:12:14 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 80 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.46 kb |
#include <math.h>
#include <cstdio>
using namespace std;
FILE *f=fopen("ciur.in", "r"), *g=fopen("ciur.out", "w");
bool v[2000005];
long i, n, j;
inline void ciur()
{
v[1]=1;
for (i=3;i<=sqrt(n);i+=2)
for (j=2;j<=n/i;j++)
v[i*j]=1;
}
inline void tipareste()
{
long k=1;
for (i=3;i<=n;i+=2)
if(!v[i])
k++;
fprintf(g, "%ld", k);
}
int main()
{
fscanf(f, "%ld", &n);
ciur();
tipareste();
fclose(f);
fclose(g);
return 0;
}