interface IStakingRewards {
  // Views
  function lastTimeRewardApplicable() external view returns (uint256);
  function rewardPerToken() external view returns (uint256);
  function earned(address account) external view returns (uint256);
  function getRewardForDuration() external view returns (uint256);
  function totalSupply() external view returns (uint256);
  function balanceOf(address account) external view returns (uint256);

  // Mutative
  function stake(uint256 amount) external;
  function withdraw(uint256 amount) external;
  function getReward() external;
  function exit() external;
}
function stake(uint256 amount) external;
// Mutative