first push

du1/program.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <ctype.h>
+
+int main() {
+    int c = 0;
+    while(1) {
+        c = getchar();
+    }
+    if (c == islower(c)) {
+        c = toupper(c);
+    }
+    else if (c == isupper(c)) {
+        c = tolower(c);
+    }
+    return 0;
+}
+
+