#include<cstdio>

#define N 1000000

int n,cnt,pri[N+],i,j,t;

long long phi[N+],s[N+];

bool v[N+];

int main(){

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

        if(!v[i]) phi[i]=i-,pri[++cnt]=i;

        for(j=;j<=cnt;++j){

            t=i*pri[j];

            if(t>N) break;

            v[t]=;

            if(i%pri[j]) phi[t]=phi[i]*(pri[j]-);

            else{phi[t]=phi[i]*pri[j];break;}

        }

    }//线性筛欧拉函数板子

    for(i=;i<=N;++i) s[i]=s[i-]+phi[i];

    while(scanf("%d",&n)){

        if(!n) break;

        printf("%lld\n",s[n]);

    }return ;

}