#pragma G++ optimize (3)
#pragma G++ optimize (2)
#include<bits/stdc++.h>
#include<ctime>
#define ll long long
using namespace std;
ll L,R;
ll fx=0;
int main(){
    scanf("%lld%lld",&L,&R);
    for(ll i=L;i<=R;i++){
        if(i%2==0){
            fx=max(fx,i/2);
        }
    }
    cout<<fx;
}

这是TLE的

#pragma G++ optimize (3)
#pragma G++ optimize (2)
#include<bits/stdc++.h>
#include<ctime>
#define ll long long
inline ll read(){
    int x=0,f=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){
        if(ch=='-')
            f=-1;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        x=(x<<1)+(x<<3)+(ch^48);
        ch=getchar();
    }
    return x*f;
}
using namespace std;
ll L,R;
ll fx=0;
int main(){
    L=read(),R=read();
    for(ll i=L;i<=R;i++){
        if(i%2==0){
            fx=max(fx,i/2);
        }
    }
    cout<<fx;
}

这是WA的

为啥会这样

题目:https://www.luogu.com.cn/problem/P8219?contestId=60992