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

int square(int a)
{
    return a*a;
}
int main() 
{
    cout<<square(5);
    return 0; 
}

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

int main() 
{
    function<int(int)> square=[&](int a){
        return a*a;
    };

    cout<<square(5);
    return 0; 
}