How To find the sum of lower Triangular matrix in C.

#include <stdio.h>

int main()

{

    int array[100][100],sum=0;

    int i=0,j=0,r,c;

    printf("Please Enter Row and Column Number: ");

    scanf("%d %d",&r,&c);

    printf("Please Enter 1st %d X %d array: 
",r,c);

    for(i=0;i<r;i++)

    {

        for(j=0; j<c; j++)

        {

            scanf("%d",&array[i][j]);

        }

    }

    /// add element

    for(i=0; i<r;i++)

    {

        for(j=0; j<c; j++)

        {

            if(j<i) /// Checking the column number is smaller then row

            {

                sum += array[i][j];

            }

        }

    }

     printf("
Sum of lower triangular matrix: %d
",sum);

    return 0;

}