UVA 10820 Send a Table 数论 欧拉函数

#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <cstring>
#include <iterator>
#include <cmath>
#include <algorithm>
#include <stack>
#include <deque>
#include <map>
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define mem0(a) memset(a,0,sizeof(a))
#define meminf(a) memset(a,-0x3f,sizeof(a))
#define fi(n) for(i=0;i<n;i++)
#define fj(m) for(j=0;j<m;j++)
#define sca(x) scanf("%d",&x)
#define scalld(x) scanf("%I64d",&x)
#define print(x) printf("%d\n", x)
#define printlld(x) printf("%I64d\n",x)
#define de printf("=======\n")
#define yes printf("YES\n")
#define no printf("NO\n")
typedef long long ll;
using namespace std;

const int maxn = 50000+100;
int phi[maxn];

void phi_table( int n ) {
    for( int i = 2; i <= n; i++ ) {
        phi[i] = 0;
    }
    phi[1] = 1;
    for( int i = 2; i <= n; i++ ) {
        if( !phi[i] ) {
            for( int j = i; j <= n; j += i ) {
                if( !phi[j] ) phi[j] = j;
                phi[j] = phi[j] / i * (i-1);
            }
        }
    }
}

int main() {
    int n;
    mem0(phi);
    phi_table(50000);
    while( sca(n) == 1 && n ) {
        if( n == 1 ) {
            printf( "1\n" );
            continue;
        }
        else {
            int res = 0;
            for( int i = 2; i <= n; i++ ) {
                res += phi[i];
            }
            printf( "%d\n", 2 * res + 1 );
        }
    }
    return 0;
}