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10820_SendaTable.cc
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10820_SendaTable.cc
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/*
*
* Author : fcbruce <fcbruce8964@gmail.com>
*
* Time : Sat 03 Sep 2016 14:56:57
*
*/
#include <cstdio>
#include <iostream>
#include <sstream>
#include <cstdlib>
#include <algorithm>
#include <ctime>
#include <cctype>
#include <cmath>
#include <string>
#include <cstring>
#include <stack>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <set>
#define sqr(x) ((x)*(x))
#ifdef _WIN32
#define lld "%I64d"
#else
#define lld "%lld"
#endif
const int INF = 0x3f3f3f3f;
const long long INFLL = 0x3f3f3f3f3f3f3f3fll;
const double PI = acos(-1.0);
const double eps = 1e-10;
typedef long long LL;
typedef int itn;
const int maxn = 50007;
const int maxm = 0;
int phi[maxn], prime[maxn];
bool isp[maxn];
int pn;
void calc()
{
memset(isp, true, sizeof isp);
isp[0] = isp[1] = false;
phi[1] = 1;
pn = 0;
for (int i = 2; i < maxn; i++)
{
if (isp[i])
{
prime[pn++] = i;
phi[i] = i - 1;
}
for (int j = 0; j < pn; j++)
{
if (i * prime[j] > maxn) break;
isp[i * prime[j]] = false;
if (i % prime[j] == 0)
{
phi[i * prime[j]] = phi[i] * prime[j];
break;
}
else
{
phi[i * prime[j]] = phi[i] * (prime[j] - 1);
}
}
}
}
LL sum[maxn];
int main()
{
#ifdef FCBRUCE
freopen("/home/fcbruce/code/t", "r", stdin);
#endif // FCBRUCE
calc();
sum[0] = 0;
for (int i = 1; i < maxn; i++) sum[i] = sum[i - 1] + phi[i];
int n;
while (scanf("%d", &n) == 1 && n > 0)
{
printf(lld "\n", (sum[n] << 1) - phi[1]);
}
return 0;
}