Cod sursa(job #522066)

Utilizator raduiris94Alexa Radu raduiris94 Data 14 ianuarie 2011 10:51:13
Problema Fractii Scor 100
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.33 kb
Raporteaza aceasta sursa 
#include<cstdio>
long long  a[1000000];
int main()
{
	FILE *f=fopen("fractii.in", "r");
	FILE *g=fopen("fractii.out", "w");
	long long rez=0, i, j; int n;
	fscanf(f, "%d", &n);
	for(i=2; i<=n; ++i)
		a[i]=i-1;
	for(i=2; i<=n; ++i)
	{
		rez+=a[i];
		for(j=i*2; j<=n; j+=i)
			a[j]-=a[i];
	}
	fprintf(g, "%Ld\n", 2*rez+1);
	return 0;
}