Why it is not working?

#1

Arrays-Wave print Column

#include
using namespace std;

int main() {
int m, n;
cin >> m >> n;
int a[m][n];
for(int i=0; i<m; i++){
for(int j=0; j<n; j++){
cin >> a[i][j];
}
}

for(int i=0; i<m; i++){
	if(i%2 == 0){
		for(int j=0; j<n; j++){
			cout << a[j][i] << ", ";
		}
	}
	else{
		for(int j=n-1; j>=0; j--){
			cout << a[j][i] << ", ";
		}
	}
}
cout << "END";
return 0;

}

Compiler shows wrong answer, while the answer is probably correct.