Untitled

void sol(){
    int n; cin >>n;
    int a[n];
    for(int i=1; i<=n; ++i) cin >> a[i];
    int x; cin >>x;
    int left=1, right=n;
    int mid;
    while(left<=right){ // neu dieu kien nay sai tuc la khong con mang nao ton tai
        mid=(left+right)/2;
        // tra ra ket qua
        if(x==a[mid]){
            cout << mid;
            return;
        }
        if(a[mid]>x){
            right = mid-1; 
        }
        else{
            left = mid+1;
        }
    }
    cout << -1;
}