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Cod sursa(job #680064)
#include<fstream>
using namespace std;
unsigned gcd(unsigned const a, unsigned const b){
return (a < b) ? gcd(b, a) : ((a % b == 0) ? b : gcd(b, a % b));
}
int main(){
ifstream in("fractii.in");
ofstream out("fractii.out");
unsigned n,i,j,s=0;
in>>n;
s+=n*2-1;
for(i=2;i<=n;i++)
for(j=2;j<=n;j++)
if(gcd(i,j)==1)
s++;
out<<s;
return 0;
}