Cod sursa(job #669687)

Utilizator andreidanAndrei Dan andreidan Data 27 ianuarie 2012 15:54:12
Problema Fractii Scor 100
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.35 kb
Raporteaza aceasta sursa 
#include <cstdio>

int a[1000005];

int main (){
	unsigned long long i,j,n,rez=0;;
	
	
	freopen("fractii.in","r",stdin);
	
	freopen("fractii.out","w",stdout);
	
	scanf("%lld", &n);
	
	for(i=1;i<=n;++i)
		a[i]=i-1;
	for(i=2;i<=n;++i){
		
		rez+=a[i];
		
		for(j=i+i;j<=n;j+=i)
			a[j]-=a[i];
	}
	
	printf("%lld", 2LL*rez+1);
	
}