diff --git a/du3/program.c b/du3/program.c
new file mode 100644
index 0000000..da2472b
--- /dev/null
+++ b/du3/program.c
@@ -0,0 +1,94 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#define STACK_SIZE 10
+
+struct stack {
+    float values[STACK_SIZE];
+    int size;
+};
+
+int is_operator(const char *str) {
+    return (strcmp(str, "+") == 0 ||
+            strcmp(str, "-") == 0 ||
+            strcmp(str, "*") == 0 ||
+            strcmp(str, "/") == 0);
+}
+
+void push_stack(struct stack *s, float value) {
+    if (s->size >= STACK_SIZE) {
+        printf("Chyba: zásobník je plný.\n");
+        exit(1);
+    }
+    s->values[s->size++] = value;
+}
+
+void p_stack(struct stack *s) {
+    for (int i = 0; i < s->size; i++) {
+        
+        (fabsf(s->values[i] - (int)s->values[i]) < 1e-6) ? 
+            printf("%d", (int)s->values[i]) : 
+            printf("%g", s->values[i]);
+
+        if (i < s->size - 1) printf(" "); 
+    }
+    printf("\n"); 
+}
+
+void p_number(float value) {
+    (fabsf(value - (int)value) < 1e-6) ? printf("%d", (int)value) : printf("%g", value);
+}
+
+
+float remove_stack(struct stack *s) {
+    if (s->size <= 0) {
+        printf("Chyba: prazdny zasobnik.\n");
+        exit(1);
+    }
+    return s->values[--s->size];
+}
+
+int main() {
+    struct stack mystack = { .size = 0 };
+    char input[100];
+
+    while (fgets(input, sizeof(input), stdin)) {
+        input[strcspn(input, "\n")] = 0;
+        if (!*input) continue;
+
+        char *endptr;
+        float value = strtof(input, &endptr);
+
+        if (endptr != input && *endptr == '\0') {
+            push_stack(&mystack, value);
+            p_stack(&mystack);
+        } else if (is_operator(input)) {
+            if (mystack.size < 2) {
+                printf("Chyba: nedostatok hodnôt v zásobníku.\n");
+                exit(1);
+            }
+
+            float b = remove_stack(&mystack);
+            float a = remove_stack(&mystack);
+
+            float res = strcmp(input, "+") == 0 ? a + b :
+                        strcmp(input, "-") == 0 ? a - b :
+                        strcmp(input, "*") == 0 ? a * b :
+                        strcmp(input, "/") == 0 ? 
+                            (b == 0 ? (printf("Chyba: delenie nulou.\n"), exit(1), 0) : a / b)
+                        : 0;
+
+            push_stack(&mystack, res);
+            p_stack(&mystack);
+        } else {
+            printf("Chyba: neplatný vstup.\n");
+            exit(1);
+        }
+    }
+
+    return 0;
+}
+
+