#include<bits/stdc++.h>

#define ri register signed

#define p(i) ++i

using namespace std;

namespace IO{

    char buf[1<<21],*p1=buf,*p2=buf,OPUT[100];

    #define gc() p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?(-1):*p1++

    template<typename T>inline void read(T &x) {

        ri f=1;x=0;register char ch=gc();

        while(!isdigit(ch)) {if (ch=='-') f=0;ch=gc();}

        while(isdigit(ch)) {x=(x<<1)+(x<<3)+(ch^48);ch=gc();}

        x=f?x:-x;

    }

    template<typename T>inline void print(T x) {

        if (x<0) putchar('-'),x=-x;

        if (!x) return putchar('0'),(void)putchar('\n');

        ri cnt(0);

        while(x) OPUT[p(cnt)]=x%10,x/=10;

        for (ri i(cnt);i;--i) putchar(OPUT[i]^48);

        return (void)putchar('\n');

    }

}

using IO::read;using IO::print;

namespace nanfeng{

    #define FI FILE *IN

    #define FO FILE *OUT

    template<typename T>inline T cmax(T x,T y) {return x>y?x:y;}

    template<typename T>inline T cmin(T x,T y) {return x>y?y:x;}

    typedef long long ll;

    static const int N=1e7+7;

    int vis[N],phi[N],prim[N],nm[N],cnt,sn;

    ll n,ans;

    inline void Getphi(int n) {

        for (ri i(2);i<=n;p(i)) {

            if (!vis[i]) phi[i]=i-1,vis[prim[p(cnt)]=i]=i;

            for (ri j(1);j<=cnt&&prim[j]*i<=n;p(j)) {

                int nw=i*prim[j];

                vis[nw]=prim[j];

                if (vis[i]==prim[j]) {

                    phi[nw]=phi[i]*prim[j];

                    break;

                }

                else phi[nw]=phi[i]*(prim[j]-1);

            }

        }

    }

    inline int main() {

        //FI=freopen("nanfeng.in","r",stdin);

        //FO=freopen("nf.out","w",stdout);

        read(n);

        sn=sqrt(n);

        Getphi(sn);

        for (ri i(2);i<=sn;p(i)) ans+=(ll)phi[i]*(n/i/i);

        print(ans);

        return 0;

    }

}

int main() {return nanfeng::main();}