#include <math.h>
#include <stdio.h>
#define eps 1e-10
#define eu 0.5772156649
long long n,m;double ans;
int main() {
scanf("%lld%lld",&n,&m);
if(n<=10000)for(register int i=1;i<=n;ans+=0.5/i,i++);
else (ans=log(n+1.0)+eu)/=2.0;
printf("%d\n",(int)((ans*=m)-=eps));
return 0; }
原文：http://www.cnblogs.com/keshuqi/p/6420707.html