How to use sum of two numbers is functions in C language

#include<stdio.h>
int sum(int x,int y); /*Function declaration*/
int main()
{
    int a,b,s;
    printf("Enter values for a and b : ");
    scanf("%d%d",&a,&b);
    s=sum(a,b);  /*Function call*/
    printf("sum of %d and %d is %d\n",a,b,s);
    return 0;
}
int sum(int x,int y)  /*Function definition*/
{
    int s;
    s = x+y;
    return s;
}