Add SB Curated (copied from the smartbugs repository).

dataset/arithmetic/tokensalechallenge.sol

@@ -0,0 +1,35 @@
+/*
+ * @source: https://smartcontractsecurity.github.io/SWC-registry/docs/SWC-101 // https://capturetheether.com/challenges/math/token-sale/
+ * @author: Steve Marx
+ * @vulnerable_at_lines: 23,25,33
+ */
+
+pragma solidity ^0.4.21;
+
+contract TokenSaleChallenge {
+    mapping(address => uint256) public balanceOf;
+    uint256 constant PRICE_PER_TOKEN = 1 ether;
+
+    function TokenSaleChallenge(address _player) public payable {
+        require(msg.value == 1 ether);
+    }
+
+    function isComplete() public view returns (bool) {
+        return address(this).balance < 1 ether;
+    }
+
+    function buy(uint256 numTokens) public payable {
+        // <yes> <report> ARITHMETIC
+        require(msg.value == numTokens * PRICE_PER_TOKEN);
+        // <yes> <report> ARITHMETIC
+        balanceOf[msg.sender] += numTokens;
+    }
+
+    function sell(uint256 numTokens) public {
+        require(balanceOf[msg.sender] >= numTokens);
+
+        balanceOf[msg.sender] -= numTokens;
+        // <yes> <report> ARITHMETIC
+        msg.sender.transfer(numTokens * PRICE_PER_TOKEN);
+    }
+}