复杂度O(1)的算法

#include <iostream>
#include <cstring>
#include <cmath>
using namespace std;
int main(){
	int n=0;
    cin>>n;
    int a = ceil(-(3.0/4.0)*n);
    float b = floor(-(5.0/7.0)*n);
    cout<<abs(b-a)+1;
}