bzoj 1968: [Ahoi2005]COMMON 约数研究

Description

Input

Output

Sample Input

Sample Output

HINT

Source

#include<cstdio>
long long n,s;
int main()
{
    scanf("%lld",&n);
    for(int i=1,j=0;i<=n;i=j+1)
    {
        j=n/(n/i);
        s+=(j-i+1)*(n/i);
    }
    printf("%lld\n",s);
}