You are given a code:

def main_solution(x):
    return (func_13(x, '_') + func_3('fot'))

Can you predict the output of `main_solution("uigzwfggrl")` without writing any code? Please reason and put your final answer in the following json format: {"output": <your output>}, where <your output> should be the final string.
user
{"ref_input": {"x": "uigzwfggrl"}, "ref_output": "u_i_g_z_w_f_g_g_r_lfot", "ref_code": "def main_solution(x):\n    return (func_13(x, '_') + func_3('fot'))", "funcname": "main_solution"}
rule