Code

#include <bits/stdc++.h>
using namespace std;
//-----------------------DEFINE-------------------------
#define __zukako__ signed main()
#define __File(name) if (fopen(name".inp", "r")) freopen(name".inp", "r", stdin), freopen(name".out", "w", stdout)
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define ll long long
#define ull unsigned long long
//-----------------------MAIN---------------------------
_zukako___{
    __File("ltp");
    ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    ll n , m , res = - 1;
    cin >> n >> m ;
    vector<ll>a(n + 1) ;
    for (int i = 1 ; i <= n ; i++) cin >> a[i] ;
    for (int i = 1 ; i <= n ; i++ )
        if (a[i] == m ){
            res = i ;
            break ;
        }
    cout << res ;
    cerr <<"Time elapsed: " <<TIME <<"s.\n";
    return (0^0);
}
@zukako

#include<bits/stdc++.h>
using namespace std;
#define int long long
signed main()
{
    int n, x; cin >> n >> x;
    vector <int> a(n + 1);
    for (int i = 1; i <= n; i++) cin>>a[i];
    auto s = lower_bound(a.begin() + 1, a.end(), x);
    if (*s != x) cout<<-1;
    else cout<<s - a.begin();
}

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