Help me in solving EZSPEAK problem

help
, ,
1

My issue

how can we debug the hidden cases

My code

#include <stdio.h>

int main() {
	char s[100];
	int i,count = 0;
	scanf("%s",s);
	for(i = 0; s[i] = '\0';i++){
     if( s[i] == 'a' ||s[i]=='e' ||s[i]== 'i' ||s[i]=='o' || s[i]=='u'){
	  count++;
	}
	}
	
	if(count >= 4){
	    printf("NO\n");
                }
      else{
          printf("YES\n");
      }
      return 0;
}

Learning course: Roadmap to 3*
Problem Link: https://www.codechef.com/learn/course/klu-roadmap-3star/KLURMP300A/problems/EZSPEAK