<>;$_=<>;y/a-h/h/;++$-while((((s/h//||s/i//)&&s/i//||s/j//||s/k//)&&s/k//||s/[l-t]//||s/u//)&&s/u//||s/[v-x]//||s/y//)&&s/y//||s/z//;print$-