Why I am getting "expected primary-expression before ‘int’ in callback function?

I have just started to learn C++. I want to call a function inside another function kinda of call back. I wrote this code. But I am getting the

error error: expected primary-expression before ‘int’
     return hello(1,2, ta(int y));
                          ^~~

Code:

#include <stdio.h>
#include <iostream>

int thirds(int x){
    return x + 1;
}

template <typename T, typename B, typename L>
int hello(T x, B y ,L z ){
    
    int first = x + 1;
    int second = y + 1;
    int third = z(5);
    
    return first + second + third;
}

int add(){
    return hello(1,1, thirds(int y));
}

int main()
{
    std::cout<<add();

    return 0;
}

Live

My expected output is 10.

Can someone tell me what need to be change? Note: I strictly need all the functions