#include<stdio.h>
int main()
{
    int first reactant,second reactant;
    scanf("%d %d",&reactant1,&reactant2);
    if(reactant1 <=0 || reactant2 <0) {
    printf("Invalid input\n");
    }
else {
    int total_mass=reactant1+reactant2;
    printf("%d\n", total-mass);
}
return 0;
}