#include<cstdio>
int n,t1,t2,t3,t4,i,s;
FILE *f,*g;
int main(){
    f=fopen("koba.in","r");
    g=fopen("koba.out","w");
    fscanf(f,"%d%d%d%d",&n,&t1,&t2,&t3);
    s=t1%10+t2%10+t3%10;
    for(i=4;i<=n;i++){
        t4=t2*t1+t3;
        s+=t4%10;
        t1=t2%10;
        t2=t3%10;
        t3=t4%10;
    }
    fprintf(g,"%d",s);

    fclose(f);
    fclose(g);
    return 0;
}