昨晚玄学wa掉一个点，实在查不出错，两个同学半小时前AC的代码，再提交也只有93了。求因并求调代码！

#include<bits/stdc++.h>
using namespace std;
long long n,a,minn=0x3f3f3f3f,ans=-0x3f3f3f3f;
int main(){
    scanf("%lld",&n);
    for(long long i=1;i<=n;i++){
        scanf("%lld",&a);
        ans=max(ans,a-minn);
        minn=min(minn,a);
    }
    printf("%lld",ans);
    return 0;
}