#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

char*mmap();
#define RD(v) int v=0;{int _c;while(_c=*rp++-48,_c>=0)v=v*10+_c;}

#define WTHI(v) {long _z=v,_n=0,_d=0;while(++_n,_d=_d<<8|0x30|_z%10,_z/=10);*(long*)wp=_d;wp+=_n;}
#define WTLO(v) {long _z=v,_n=8,_d=0;while(_d=_d<<8|0x30|_z%10,_z/=10,--_n);*(long*)wp=_d;wp+=8;}
#define WT(v) if(v>=100000000){WTHI(v/100000000);WTLO(v);}else{WTHI(v);}

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	RD(n);
	char*cp=rp;
	rp+=n+1;
	long s=0,min=0,max=0,v=0;
	for(int i=0;i<n;++i){
		int neg=*cp++=='B'^(*rp=='-'&&++rp);
		RD(a);
		s+=neg?-a:a;
		min=min<=s?min:s;
		max=max>=s?max:s;
		v=v>=max-min?v>=min-max?v:min-max:max-min;
	}
	char wbuf[16],*wp=wbuf;
	WT(v);
	write(1,wbuf,wp-wbuf);
	_exit(0);
}