#include <iostream>
using namespace std;
int main()
{
    int n, a[10000], x, i;
    cin >> n;
    for (i=0; i<n; i++) cin >> a[i];
    cin >> x;
    for (i=0; i<n; i++){
        if (a[i] == x){
            cout << i+1 << endl;
            return 0;
        }
    }
    cout << "-1" << endl;
    return 0;
}

#include <iostream>
#include <stack>
#include <cmath>
#include <vector>
#include <string.h>
#include <queue>
#include <stdio.h>
#include <iomanip>
#include <cstdio>
#include <algorithm>
#define int long long
using namespace std;
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a[N];
signed main()
{
	int n, x;
	cin >> n;
	for(int i = 1; i <= n; i++)
	{
		cin >> a[i];
	}
	cin >> x;
	for(int i = 1; i <= n; i++)
	{
		if(a[i] == x)
		{
			cout << i << endl;
			return 0;
		}
	}
	cout << "-1" << endl;
	return 0;
}

一个-1都没有

所以用这个也能过

#include <iostream>
#include <stack>
#include <cmath>
#include <vector>
#include <string.h>
#include <queue>
#include <stdio.h>
#include <iomanip>
#include <cstdio>
#include <algorithm>
#define int long long
using namespace std;
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a[N];
signed main()
{
	int n, x;
	cin >> n;
	for(int i = 1; i <= n; i++)
	{
		cin >> a[i];
	}
	cin >> x;
	for(int i = 1; i <= n; i++)
	{
		if(a[i] == x)
		{
			cout << i << endl;
			break;
		}
	}
	return 0;
}