#include 
                  int sum_of_even(int x);
                  int main()
                  {
                    int x=0,sum=0;
                    sum+=sum_of_even(x);
                    printf("%d",sum);
                    
                    return 0;
                  }
                  int sum_of_even(int x)
                  {
                    int sum=0;
                    for(;x<=20;x+=2)
                    {
                      sum+=x;
                    }
                    return sum;
                  }