build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'
        classpath 'com.google.gms:google-services:3.1.1'
    }

    ext {
        compileSdkVersion = 22
        buildToolsVersion = "25.0.3"
    }
}