6 Standard Deviation continuous series

#include <stdio.h>
#include <math.h>
const int MAX_SIZE = 25;

void StandardDeviation(int ci[][2], int fre[], int n){
    int mid[n];
    for(int i=0 ; i<n ; i++){
        mid[i] = (ci[i][0]+ci[i][1])/2;
    }

    long long int sum =0 , N=0;
    for(int i=0 ; i<n ; i++){
        sum += (fre[i]*mid[i]);
        N += fre[i];
    }

    float mean = (float)sum / (float)N ;

    long int sumk = 0;

    for(int i=0 ; i<n ; i++){
        float temp = mid[i] - mean;
        sumk += ( (temp*temp) * fre[i] );
    }

    float standard_dev = (float) sumk / (float) N;
    standard_dev = sqrt(standard_dev);
    printf("\nStandard deviation is %.3f \n",standard_dev);
}

int main()
{
    int n;
    int ci[MAX_SIZE][2],fre[MAX_SIZE];
    printf("Enter the number of elements \n");
    scanf("%d",&n);


    printf("\nEnter CI one by one \n");
    for(int i=0 ; i<n ; i++){
        for(int j=0 ; j<2 ; j++){
            scanf("%d",&ci[i][j]);
        }
    }

    printf("\nNow enter the %d frequencies : \n",n);
    for(int i=0 ; i<n ; i++){
        scanf("%d",&fre[i]);
    }

    // now calling function which will print the standard deviation
    StandardDeviation(ci, fre, n);

    return 0;
}