1.số

#include <bits/stdc++.h>
using namespace std;

const int nmax = 1e6 + 1;

long long n, s = 0;
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> n;
    while (n)
    {
        s = s * 10 + (n % 10);
        n /= 10;
    }
    cout << s;
}

2.xâu

#include <bits/stdc++.h>
using namespace std;

const int nmax = 1e6 + 1;

string s;

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> s;
    reverse(s . begin(), s . end());
    cout << s;
}

n=input()
print(n[::-1])