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pragma solidity 0.4.18;

// Contract to test unsigned integer underflows and overflows
// note: uint in solidity is an alias for uint256

// 1.Overflow Sample Test
//  1) Overflow_contract Deploy
//  2) max call        -> 2**256-1
//  3) overflow() call -> overflow excute
//  4) max call        -> 0

// 2. Underflow Sample Test
//. 1) Underflow_contract Deploy
//  2) zero call        -> 0
//  3) underflow() call -> overflow excute
//  4) zero call        -> 2**256-1

contract Overflow_contract {
    uint public max = 2**256-1;    
    // max will end up at 0
    function overflow() public {
        max += 1;
    }
}

contract Underflow_contract {

uint public zero = 0;
    // zero will end up at 2**256-1
    function underflow() public {
        zero -=  1;
    }
}

contract OffByOne_contract {
    uint[] public arr = [1, 1, 1, 1, 1];