very simple calc function in C

#include <stdio.h>


int main(int argc, char *argv[]) {
int n1, n2, sum;

printf("enter a: ");
scanf("%d", &n1);

printf("enter b: ");
scanf("%d", &n2);

sum = addnum(n1, n2);
printf("sum = %d",sum);
return 0;
}

int addnum(int a,int b){
int res = a + b;
return res;
}