everything is a lambda no matter how much I have to shoehorn

#include <iostream>
#include <functional>

using namespace std;

function<int(int)> trysumore = [](int a) {
    return a*a;
};

auto trysum = [](int a) -> int {
    return a*a;
};

int main(int argc, char **argv){
    cout << trysum(3);
    cout << "\n";
    cout << trysumore(4);
}