diff --git a/index.js b/index.js
index 3bb4d07..c695d1e 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,43 @@
  * Depending on the operation, either add up all of the numbers or subtract all of the numbers, from left to right.
  * @returns {number} The result of either adding all numbers or subtracting all numbers, depending on the arguments added to the command line.
  */
-function calculator() {}
+function calculator() {
+    console.log(process.argv)
+    let sum;
+    let operations = process.argv[2];
+    let emptyArr = []
+    let indexOfInfo = process.argv
+
+    if (indexOfInfo.length <= 2) {
+        return `No operation provided...`
+    }
+    else if (indexOfInfo.length <= 3) {
+        return `No numbers provided...`
+    }
+
+    else if (operations === "plus") {
+        for (let i = 3; i < indexOfInfo.length; i++) {
+            let num = indexOfInfo[i]
+            emptyArr.push(num)
+            sum = emptyArr.reduce((prev, curr) => Number(prev) + Number(curr))
+        }
+        return sum
+    }
+    else if (operations === "minus") {
+        for (let i = 3; i < indexOfInfo.length; i++) {
+            let num = indexOfInfo[i]
+            emptyArr.push(num)
+            sum = emptyArr.reduce((prev, curr) => Number(prev) - Number(curr))
+        }
+        return sum
+    }
+    else if (operations !== "plus" || "minus") {
+        return `Invalid operation: ${operations}`
+    }
+}
+
+calculator()
+
 
 // Don't change anything below this line.
 module.exports = calculator;