diff --git a/letter-grade.c b/letter-grade.c
index f05ffbc..ae6f968 100644
--- a/letter-grade.c
+++ b/letter-grade.c
@@ -5,19 +5,24 @@ int main() {
     scanf("%i", &input);
     printf("Your input was: %i\n", input);
 
-    char letter;
-    if ((input/10) >= 9) {
-        letter = 'A';
-    } else if ((input/10) >= 8) {
-        letter = 'B';
-    } else if ((input/10) >= 7) {
-        letter = 'C';
-    } else if ((input/10) >= 6) {
-        letter = 'D';
+    if ((input >= 0) && (input <= 100)) {
+        char letter;
+        if ((input/10) >= 9) {
+            letter = 'A';
+        } else if ((input/10) >= 8) {
+            letter = 'B';
+        } else if ((input/10) >= 7) {
+            letter = 'C';
+        } else if ((input/10) >= 6) {
+            letter = 'D';
+        } else {
+            letter = 'F';
+        }
+        printf("Your letter grade is %c\n", letter);
     } else {
-        letter = 'F';
+        printf("ERROR: Input must be no more than 100 and no less than 0\n");
+        return 1;
     }
 
-    printf("Your letter grade is %c\n", letter);
     return 0;
 }
\ No newline at end of file