UVA10820SendATable

//UVA10820SendATable#include<cstdio>#include<cstring>#include<cmath>const int maxn = 50000;int phi[maxn + 5];long long f[maxn + 5];void phi_table(int n, int *phi) {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) {//相当于筛法     if(!phi[j]) phi[j] = j;    phi[j] = phi[j] / i * (i - 1);}} int main() {phi_table(maxn, phi);int n;for(int i = 2; i <= maxn; i++) f[i] = f[i - 1] + phi[i];while(scanf("%d", &n) == 1 && n) printf("%lld\n", 2 * f[n] + 1);return 0;}/*250*/