2017-2018 ACM-ICPC Pacific Northwest Regional Contest (Div. 2) P- Fear Factoring

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分析：        

题目比较有意思，这么转换就比较好求解了~

代码如下:

#include 
#include 
#include 
using namespace std;

typedef unsigned long long LL;
LL a,b;

LL func(LL n){
    if ( n == 0) return 0;
    LL ans = 0;
    LL t = 0;
    for (LL i=1; i<=n; i=t+1) {
         t = n/(n/i);
         ans += (i+t)*(t+1-i)/2*(n/i);
    }
    return ans;
}

int main(){
    while (scanf("%lld%lld",&a,&b)==2) {
        printf("%lld\n",func(b)-func(a-1));
    }
    return 0;
}