WA20pts，希望知道此做法为什么有问题

#include<bits/stdc++.h>
#define INF 1e16
#define endl '\n'
#define PI acos(-1)
#define pb push_back
#define int long long
#define mem(x,v) memset(x,v,sizeof x)
using namespace std;
const int N = 1e5+5;
inline int read(){
	register int x=0,f=1;register char c=getchar();
	while(c>'9'||c<'0'){if(c=='-')f=-1;c=getchar();}
	while(c>='0'&&c<='9')x=(x<<1)+(x<<3)+(c^48),c=getchar();
	return x*f;
}

int n,sum,ans,a[N];

signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=1;i<=n;i++){
		if(a[i]>a[i-1])sum++,ans=max(ans,sum);
		else sum=0;
	}
	cout<<ans;
	return 0;
}