error CS1525: unexpected symbol `.' | how can I fix this code?

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

public class Cronometer : MonoBehaviour { public Text timerText; public Text gameoverText; private float startTime;

 // Use this for initialization
 void Start()
 {
     startTime = Time.time;

 }

 // Update is called once per frame
 void Update()
 {
     float t = Time.time - startTime;

     string minutes = ((int)t / 60).ToString();
     string seconds = (t % 60).ToString("f0");

     timerText.text = minutes + ":" + seconds;
     if (seconds > 15)
     {.ToString("f0");
     }

     gameoverText.text = "You Lost";
 }

}