diff --git a/du3/program.c b/du3/program.c
index 8dac2b5..fd8c1fa 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -17,7 +17,8 @@ int main() {
         int eq_index = 0;
         int index = 0;
         while (fgets(buffer, sizeof(buffer), stdin) != NULL) {
-                if (buffer[0] == '\n') break;
+                int error = 0;
+		if (buffer[0] == '\n') break;
                 index = 0;
                 eq_index = 0;
                 int eq_operand_length = 0;
@@ -27,6 +28,12 @@ int main() {
                                 index++;
                                 continue;
                         }
+			if (isalpha(buffer[index]) && !error) {
+				error = 1;
+				strcpy(output[output_length], "CHYBA");
+				output_length++;
+
+			}
                         if (isdigit(buffer[index]) || (buffer[index] == '.' && eq_operand_length > 0 && isdigit(buffer[index + 1])) || (buffer[index] == '-' && (eq_operand_length == 0 || strchr("+-*/=", buffer[index - 1])))) {
                                 equation[eq_index][eq_operand_length] = buffer[index];
                                 eq_operand_length++;
@@ -47,13 +54,13 @@ int main() {
                         equation[eq_index][eq_operand_length] = '\0';
                         eq_index++;
                 }
-
                 float total = 0.0;
                 char last_operator = '+';
                 int sign = 0;
                 int n_of_signs = 0;
                 char operators[6] = "+-=*/";
-                for (int i=0;i<eq_index;i++) {
+                if (!error) {
+		for (int i=0;i<eq_index;i++) {
                         n_of_signs = 0;
                         for (int l=0; l<5;l++) {
                                 if (strchr(equation[i], operators[l]) != NULL) {
@@ -78,7 +85,6 @@ int main() {
                                                         total = divided(total, atof(equation[i]));
                                                         break;
                                                 case '=':
-                                                        //total = round(total * 100) / 100;
                                                         if (fabs((round(total * 100) / 100) - atof(equation[i])) < 1e-6) {
                                                                 strcpy(output[output_length], "OK");
                                                                 output_length++;
@@ -98,6 +104,7 @@ int main() {
                         }
                         sign = !sign;
                 }
+		}
                 memset(equation, 0, sizeof(equation));
 		//printf("%f - %f\n",total, (round(total * 100) / 100));
         }