#include <stdio.h>
#define Nmax 1000000

int phi[Nmax+1];

main(){

freopen("fractii.in", "r", stdin);
freopen("fractii.out", "w", stdout);

int N, i, j;
long long sum = 0;

scanf("%d", &N);

for(i=1; i<=Nmax; i++){
    phi[i] = i-1;
}
for(i=2; i<=Nmax; i++){
    for(j=2*i; j<=Nmax; j+=i){
        phi[j] -= phi[i];
    }
}phi[0] = phi[1] = 1;

for(i=1; i<=N; i++){
    sum += phi[i];
}sum *= 2; sum--;

printf("%lld", sum);

return 0;
}


/*PHI[i]

for(i=1; i<=Nmax; i++){
    phi[i] = i;
}
for(i=2; i<=Nmax; i++){
    if(phi[i]==i){
        for(j=i; j<=Nmax; j+=i){
            phi[j] /=i;
            phi[j] *= (i-1);
        }
    }
    phi[j] /= i;
    phi[j] *= (i-1);
}

*/