Sum of 1^2+2^2+3^2+...n^2 using C language

#include<stdio.h>
int main()
{
 int a,n,sum=0;
 printf("enter the value of n :");
 scanf("%d",&n);
 for(a=1;a<=n;a++)
 {
  sum=sum+(a*a);
 }
 printf("sum=%d",sum);
 return 0;
}