diff --git a/du3/program.c b/du3/program.c
new file mode 100644
index 0000000..fa55952
--- /dev/null
+++ b/du3/program.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+
+int main() {
+    char line[256];
+
+    while (fgets(line, sizeof(line), stdin) != NULL) {
+        if (line[0] == '\n' || line[0] == '\r') break;
+
+        double a, b, result;
+        char op;
+        char eq;
+        char extra;
+
+        int n = 0;
+        int parsed = sscanf(line, " %lf %c %lf %c %lf %c%n", &a, &op, &b, &eq, &result, &extra, &n);
+
+        if (parsed != 5 || eq != '=') {
+            printf("CHYBA\n");
+            continue;
+        }
+
+        if (op != '+' && op != '-' && op != '*' && op != '/') {
+            printf("CHYBA\n");
+            continue;
+        }
+
+        if (op == '/' && b == 0.0) {
+            printf("CHYBA\n");
+            continue;
+        }
+
+        double actual;
+        if      (op == '+') actual = a + b;
+        else if (op == '-') actual = a - b;
+        else if (op == '*') actual = a * b;
+        else                actual = a / b;
+
+        double rounded_actual = round(actual * 100.0) / 100.0;
+        double rounded_result = round(result * 100.0) / 100.0;
+
+        if (fabs(rounded_actual - rounded_result) < 1e-9) {
+            printf("OK\n");
+        } else {
+            printf("ZLE\n");
+        }
+    }
+
+    return 0;
+}