diff --git a/a1/program.c b/a1/program.c
new file mode 100644
index 0000000..f676107
--- /dev/null
+++ b/a1/program.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int main() {
+    int lines=0;
+    char symbol;
+    while ((symbol=getchar()) !=EOF) {
+        if (symbol>= 'A' && symbol <= 'Z') {
+            putchar(symbol+32);
+        } else { if (symbol >= 'a' && symbol <= 'z') {
+            putchar(symbol-32);
+        } else { putchar(symbol); }
+        }
+        if (symbol == '\n') {
+            lines++;
+        }
+    }
+    printf("Number of lines:%d\n", lines);
+    return 0;
+}
\ No newline at end of file