咋只有70分？

#include <bits/stdc++.h>
using namespace std;

int main() {
    int a,b;
    cin>>a>>b;
    if(a%2==1 || b%2==1){cout<<(a/2)+(b/2);}                        
    if(a%2==1 && b%2==1){cout<<(a/2)-(b/2);} 
    if(a%2==0 && b%2==0){cout<<(b-a-1)/2;} 
	
         
         
      return 0;
}