System.setProperty("webdriver.gecko.driver", "C:\Severs.exe");
WebDriver driver = new FirefoxDriver();

Exception in thread "main" java.lang.IllegalStateException: The driver executable does not exist: C:Severs.exe
    at com.google.common.base.Preconditions.checkState(Preconditions.java:199)
    at org.openqa.selenium.remote.service.DriverService.checkExecutable(DriverService.java:121)
    at org.openqa.selenium.remote.service.DriverService.findExecutable(DriverService.java:116)
    at org.openqa.selenium.firefox.GeckoDriverService.access$000(GeckoDriverService.java:37)
    at org.openqa.selenium.firefox.GeckoDriverService$Builder.findDefaultExecutable(GeckoDriverService.java:95)
    at org.openqa.selenium.remote.service.DriverService$Builder.build(DriverService.java:296)
    at org.openqa.selenium.firefox.FirefoxDriver.createCommandExecutor(FirefoxDriver.java:277)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:247)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:242)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:238)
    at org.openqa.selenium.firefox.FirefoxDriver.<init>(FirefoxDriver.java:127)
    at com.first.selenium1.LaunchBrowser.main(LaunchBrowser.java:12)