<input type="hidden" name="problem" value="<tmpl_var id>">
<tmpl_if_defined contest><input type="hidden" name="contest" value="<tmpl_var contest>"></tmpl_if_defined>
<label>File: <input name="prog" required type="file"></label>
<input type="hidden" name="problem" value="<tmpl_var id>">
<tmpl_if_defined contest><input type="hidden" name="contest" value="<tmpl_var contest>"></tmpl_if_defined>
<label>File: <input name="prog" required type="file"></label>