diff --git a/index.js b/index.js
index 3bb4d07..78b7f9a 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,41 @@
  * 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)
+   // console.log(process.argv[2])
+    let calOperation = process.argv[2]
+    let indexOf = process.argv
+    let sum;
+    let arr = [];
+   // let calOp4 =  process.argv[4]
+   // let calOp5 =  process.argv[5]
+        if(indexOf.length <= 2 ){
+        return "No operation provided..."  
+    }
+    else if (indexOf.length <= 3){
+        return "No numbers provided..."
+    }else if (calOperation === "plus"){
+        for (let i = 3; i < indexOf.length; i++){
+            let num = indexOf[i]
+            arr.push(num)
+            sum = arr.reduce((prev, curr)=> Number(prev) + Number (curr))
+        }
+        return sum;
+    }
+    else if(calOperation === 'minus'){
+        for(let i = 3 ;i < indexOf.length; i++){
+            let num = indexOf[i]
+            arr.push(num)
+            sum = arr.reduce((prev, curr)=> Number(prev) - Number (curr))
+        }
+         return sum;
+        }
+        else if (calOperation !== ("plus"||'minus')){
+            return `Invalid operation: ${calOperation}`
+        }
+    }
 
+    calculator()
 // Don't change anything below this line.
 module.exports = calculator;