#include<stdio.h>
int main(){
    long long mass1,mass2,total_mass;
    int input_status1,input_status2;
    printf("Enter the mass of the first reactant:");
    input_status1=scanf("%lld",&mass1);
    printf("Enter the mass of the second reactant:");
    input_status2=scanf("%11d",&mass2);
    if(input_status1 !=1 || input_status2 !=1 || mass1<0 || mass2<0){
        printf("Invalid Input\n");
    }else{
}
total_mass=mass1 + mass2;
printf("%lld\n",total_mass);
}
return 0;
}