delete pics to save space

2.10820.cpp

@@ -0,0 +1,20 @@
+#include<cstdio>
+const int maxn=50000;
+int n,i,j,phi[maxn+5],sum[maxn+5];
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	phi[1]=1;
+	for(i=2;i<=maxn;i++)
+		if(!phi[i])
+			for(j=i;j<=maxn;j+=i)
+			{
+				if(!phi[j]) phi[j]=j;
+				phi[j]=phi[j]/i*(i-1);
+			}
+	for(i=1;i<=maxn;i++) sum[i]=sum[i-1]+phi[i];
+	while(scanf("%d",&n)==1&&n) printf("%d\n",2*(sum[n]-1)+1);
+	return 0;
+}