diff --git a/cv3/program.c b/cv3/program.c
index 46bb6e7..c95d720 100644
--- a/cv3/program.c
+++ b/cv3/program.c
@@ -55,10 +55,16 @@ int main() {
                 }
         }
         else {
-            p = atof(line);
-            number[a].cislo = p;
-            a++;
-            input++;
+            if(line[0] >= 'a' && line[0] <= 'z') {
+                p = atof(line);
+                number[a].cislo = p;
+                a++;
+                input++;
+            }
+            else {
+                printf("bad input");
+                break;
+            }
         }
 
         for (i = 0; i < a; i++){