diff --git a/program.c b/program.c
new file mode 100644
index 0000000..74abb87
--- /dev/null
+++ b/program.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <ctype.h>
+
+int main() {
+    int c;
+    int lines = 0;
+
+    while ((c = getchar()) != EOF) {
+        if (islower(c)) {
+            putchar(toupper(c));
+        } else if (isupper(c)) {
+            putchar(tolower(c));
+        } else if (c == '\n') {
+            putchar(c);
+            lines++;
+        } else if (isprint(c)) {
+            putchar(c);
+        }
+    }
+
+    printf("\nRiadky: %d\n", lines);
+    return 0;
+}