...

include <bits/stdc++.h>

define int long long

using namespace std;
main()
{
string s;
cin>>s;
for(int i=s.size();i>=0;i--)
cout<<s[i];
}

include<bits/stdc++.h>

define ll long long

define ch char

define str string

define FOR(i, a, b) for(int i = (a); i<= (b); i++)

const int N = 1E6+2;

using namespace std;

ll n, k, a[N];

int main()
{

cin >> n >> k;
FOR(i, 1, n)
{
    cin >> a[i];
}
sort(a + 1, a + n + 1);
int dem = 0, tong = 0;
FOR(i, 1, n-1)
{
    FOR(j, i+1, n)
    {
        if(a[i] <= k && a[j] <= k)
        {
            tong = a[i] + a[j];
            if(tong == k)
            {
                dem++;
                tong = 0;
            }
        }
    }
}

cout << tong << " " << dem;

return 0;

}

include <bits/stdc++.h>

using namespace std;

int n, ans;
int a[100005], L[100005];

int main()
{
cin >> n;
for(int i = 1; i <= n; ++i) cin >> a[i];
for(int i = 1; i <= n; ++i) L[i] = 1;
for(int i = 1; i <= n; ++i)
{
for(int j = 1; j < i; ++j)
{
if(a[i] > a[j]) L[i] = max(L[i], L[j] + 1);
}
}
ans = 1;
for(int i = 1; i <= n; ++i) ans = max(L[i], ans);
int d = 0;
for(int i = 1; i <= n; ++i)
{
if(L[i] == ans) ++d;
}
cout << d;
}

Hoc gioi!