#include<stdio.h>
int main()
{
    int a,b,total-mass;
    scanf("%d",&a);
    scanf("%d",&b);
    total-mass=a+b;
    if(a<=0)
    {
        printf("invalid input\n");
    }
    else
    {
        printf("%d",total-mass);
    }
    return 0;
}