为什么自己的编译器能编译，洛谷编译失败

#include<bits/stdc++.h>
using namespace std;
int main(){
	int a[26] = {0},max,len;
	char z[400];
	for(int i = 0;i < 4;i++){
		gets(z);
		len = strlen(z);
		for(int i = 0;i < len;i++){
			if(z[i] >= 'A'&&z[i] <= 'Z'){
				a[z[i]-'A']++; 
			}
		}	
	} 
	for(int i = 0; i < 26;i++) max = max > a[i]?max:a[i]; 	
	for(int i = max;i > 0;i--){
		for(int j = 0;j < 26;j++){
			if(a[j] >= i) cout<<"* ";
			else cout<<"  ";
		}
		cout<<endl;
	}
	cout<<"A B C D E F G H I G K L M N O P Q R S T U V W X Y Z"<<endl;
	return 0;
}