#include<stdio.h>
int main()
{
    int a,b,c;
   if(scanf("%d %d %d",&a,&b,&c)!=2)
   {
       printf("Invalid input");
       return 0;
   }
    if(a<0 || b<0 )
    {
        printf("Invalid input");
    }
    else
    {
        (printf("%d\n",a+b+c);
    }
    return 0;
}