diff --git a/index.js b/index.js
index 3bb4d07..c501926 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,28 @@
  * 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() {
+    const[, , theOperator, numOne, numTwo] = process.argv;
+    for(const index of process.argv){
+        if(process.argv[2] === "plus"){
+        return Number(process.argv[3]) + Number(process.argv[4])
+        }
+        else if(process.argv[2] === "minus"){
+         return Number(process.argv[3]) - Number(process.argv[4])
+        }
+     for(const indexes of process.argv){
+        if(!process.argv[2]){
+            return "No operation provided..."
+        }
+        else if(!process.argv[3]){
+            return "No numbers provided..."
+        }
+        else if(process.argv[2] !== ("plus" || "minus")){
+            return "Invalid operation: modulo"
+        }
+    }   
+}
+}
 
 // Don't change anything below this line.
 module.exports = calculator;