usaco Electric Fence

这种有小数的题目总会令我格外头疼。

/*
ID: modengd1
PROG: fence9
LANG: C++
*/
#include <iostream>
#include <stdio.h>
#include <memory.h>
#include <math.h>
using namespace std;
long long ans,x1,x2;
int n,m,p;
int main()
{
    freopen("fence9.in","r",stdin);
    freopen("fence9.out","w",stdout);
    scanf("%d%d%d",&n,&m,&p);
    ans=0;
    for(int i=1;i<m;i++)
    {
        x1=(double)n*i/m;
        x2=p-double(p-n)/m*i;
        if((p-n)*i%m==0)//(p-n)*i/m是整数
            x2--;
        ans+=x2-x1;
    }
    cout<<ans<<endl;
    return 0;
}