#include<stdio.h>
int f()
{
    char s[10],ch=0;
    int k,sum=0;
    while((ch=getchar())&&ch!='\n')
    {
    	if(ch==' ') continue;
        if(ch==']') {ungetc(ch,stdin);break;}
        scanf("%s%d",&s,&k);
        if(ch=='R') 
        {
            getchar();
            sum+=k*f();
            getchar();
        }
        if(ch=='B') sum-=k;
    	if(ch=='F') sum+=k;
    }
    return sum;
}
int main()
{
    int ans=f();
    if(ans) printf("%d",ans);
    else printf("%d",-ans);
    return 0;
}