How do I make the player heat up?

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C#

script

what i mean by this, is that im trying to make a script for a survival game, when the player runs he heats up. ive got the UI all set up its just the script that needs work.

it keeps saying: "(19,27) Math does not exist in current context"
and
"(29,27) Math does not exist in current context"

what should i do to make it work?

heres the script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Temperature : MonoBehaviour
{
    public float minTemperature = 32;
    public float temperature = 32;
    public float maxTemperature = 105;
    
    public float temperatureFactor = 30;
    public bool overheating;
    void Update()
    {
        float tempChange = Time.deltaTime * temperatureFactor;
        if (Input.GetKey(KeyCode.LeftShift) && !overheating)
        {
            temperature = Math.Min(maxTemperature, temperature + tempChange);
            if (temperature == maxTemperature)
            {
                overheating = true;
            }
        }
        else if (!Input.GetKey(KeyCode.W))
        {
            temperature = Math.Max(minTemperature, temperature - tempChange);
            if (temperature == minTemperature)
            {
                overheating = false;
            }
        }
    }
}

What I have tried:

ive surfed the internet for answers but i couldn,t find anything