How to solve leetcode judging systems, it keeps giving me an error in a non-existing lines

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
int* twoSum(int* nums, int numsSize, int target, int* returnSize);


int* twoSum(int* nums, int numsSize, int target, int* returnSize)
{
    int i,j, k= 0;

    for(i=0; i<numsSize; i++)
    {
        for(j= i+1; j<numsSize; j++)
        {
            if((nums[i]+nums[j])== target)
            {
                nums[k]= i;
                k++;
                nums[k]= j;
            }
            else
                printf("Target Not Found!!\n");
        }
    }
    *returnSize= k;

    return nums;
}

int main()
{
    int n;
    printf("Please enter the number of elements exist in the array entered: ");
    scanf("%d", &n);
    int arr[n]; 
    int i;

    for(i=0; i<n; i++)
    {
        printf("Array element no.%d: ",i);
        scanf("%d", &arr[i]);
    }

    for(i=0; i<n; i++)
    {
        printf("Array element no.%d: %d\n",i, arr[i]);
    }

    int target;
    printf("Please Enter the target you want: ");
    scanf("%d", &target);

    int size;
    int* result = twoSum(arr, n, target, &size);

    for(i=0; i<2; i++)
    {
        printf("Array element no.%d: %d\n",i, arr[i]);
    }
    return 99;
}

Line 63: Char 5: error: redefinition of ‘main’ [solution.c]
 int main(int argc, char *argv[]) {
     ^~~~