C++,90 #2出错了

#include <iostream>
using namespace std;
int main()
{
	int x;
	int n;
	unsigned long long length;
	cin >>x;
	cin >> n;
	if(1<=x&&x<=5)
	{
		length=(5-x+1)*250+(n-((7-x)+1))/7*1250+(n-((7-x)+1))%7*250;
		cout << length <<endl;
	}
	else if(6<=x&&x<=7)
	{
		length=(n-((7-x)+1))/7*1250+(n-((7-x)+1))%7*250;
		cout << length <<endl;
	}
	else
	{
		cout << "Error." << endl;
	}
	
	return 0;
}