diff --git a/factorial.cpp b/factorial.cpp
index b27b86a..2c249de 100644
--- a/factorial.cpp
+++ b/factorial.cpp
@@ -7,6 +7,10 @@ int main() {
     cout << "Enter a positive integer: ";
     cin >> n;
 
+    if(n < 0){
+        cout << "you can't enter negative integer";
+        return -1;
+    }
     for(int i = 1; i <= n; ++i) {
         factorial *= i;
     }