#include <stdio.h>
#include <stdlib.h>

__global__ void add (int a, int b, int *res){
  *res = a + b;
}

int main(){
  int res = 0;
  int d_res = NULL;

  add<<<1,1>>>(2,2, d_res);
  cudaMemcpy(&res, d_res, sizeof(int), cudaMemcpyDeviceToHost);

  printf("2 + 2 = %d\n", res);

  return EXIT_SUCCESS;
}