#include (stdio.h>)
int main(){
    int q1,p1,q1,p2,q3,p3;
    if(scanf("%d %d %d %d %d %d", &q1,&p1,&q2,&p2,&q3,&p3) 1=6){
        printf("Invalid input\n");
    }else if (q1 < 0 || p1 < 0 || q2 < 0 || p2 < 0 || q3 < 0 || p3 < 0){
        printf("Invalid Input\n");
    }else{
        long long total -(long long)q1 * p1 +(long long)q2 * p2 +(long long)
        q3 +p3;
        printf("%11d\n", total);
    }
    return 0;
}