#include<stdio.h>
int N, fi[1000100];
long long ret;

int main() {
    
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&N);
    for(int i=1;i<=N;++i) {
        fi[i]=i;
    }

    for(int i=1;i<=N;++i) {

        ret += fi[i];
        for(int j=2;i*j<=N;++j) {
            fi[i*j]-=fi[i];
        }
    }
   
    printf("%lld",2*ret-1);
    return 0;
}