diff --git a/du3/program.c b/du3/program.c
new file mode 100644
index 0000000..41206a4
--- /dev/null
+++ b/du3/program.c
@@ -0,0 +1,104 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <ctype.h>
+
+#define STACK_SIZE 10
+#define LINESIZE 100
+
+struct stack {
+    float values[STACK_SIZE];
+    int size;
+};
+
+//zakladne funkcie
+
+void push_stack(struct stack *s, float value) {
+    if (s->size >= STACK_SIZE) {
+        printf("Chyba: zasobnik je plny.\n");
+        exit(1);
+    }
+    s->values[s->size] = value;
+    s->size++;
+}
+
+float pop_stack(struct stack *s) {
+    if (s->size <= 0) {
+        printf("Chyba: zasobnik je prazdny.\n");
+        exit(1);
+    }
+    s->size--;
+    return s->values[s->size];
+}
+
+void print_stack(struct stack *s) {
+    for (int i = 0; i < s->size; i++) {
+        if (i > 0) printf(" ");
+        printf("%g", s->values[i]);
+    }
+    printf("\n");
+}
+
+//pomocne funkcie
+
+//je retazec cislo
+int is_number(const char *str) {
+    char *endptr;
+    strtof(str, &endptr);
+    // ak endptr ukazuje na koniec retazca, bolo to cele cislo
+    return (*str != '\0' && *endptr == '\0');
+}
+
+
+int main(void) {
+    struct stack s;
+    memset(&s, 0, sizeof(struct stack));
+
+    char line[LINESIZE];
+
+    while (fgets(line, sizeof(line), stdin)) {
+        line[strcspn(line, "\n")] = '\0';
+
+        //preskocit prazdny riadok
+        if (strlen(line) == 0)
+            continue;
+
+        if (is_number(line)) {
+            float value = strtof(line, NULL);
+            push_stack(&s, value);
+        } else if (strlen(line) == 1 && strchr("+-*/", line[0])) {
+            //operacia
+            if (s.size < 2) {
+                printf("Chyba: nedostatok operandov.\n");
+                return 1;
+            }
+            float b = pop_stack(&s);
+            float a = pop_stack(&s);
+            float result;
+
+            switch (line[0]) {
+                case '+': result = a + b; break;
+                case '-': result = a - b; break;
+                case '*': result = a * b; break;
+                case '/':
+                    if (b == 0) {
+                        printf("Chyba: delenie nulou.\n");
+                        return 1;
+                    }
+                    result = a / b; break;
+                default:
+                    printf("Chyba: neznama operacia.\n");
+                    return 1;
+            }
+            push_stack(&s, result);
+        } else {
+            printf("Chyba: neplatny vstup.\n");
+            return 1;
+        }
+
+        print_stack(&s);
+    }
+
+    return 0;
+}