Help me in solving MATDIAGSUM problem

help
,
1

My issue

it is giving runtime error, i don’t understand why

My code

#include <stdio.h>
void main()
{
    int n;
    scanf("%d",&n);//order of matrix
    int a[n][n],sum=0;
    for(int i=0;i<n;i++)
    {
        for (int j=0;j<n;j++)
        {
            scanf("%d",&a[i][j]);
        }
    }
    for(int i=0;i<n;i++)
    {
        for (int j=0;j<n;j++)
        {
            if (i==j || i+j==n-1)
            sum=sum+a[i][j];
        }
    }
    printf("%d",sum);
}

Learning course: BCS301: Data structures
Problem Link: https://www.codechef.com/learn/course/abesit-dsa/ABESITDS09/problems/MATDIAGSUM