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

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

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	int RD(n);
	long RD(x);
	x*=1-n;
	do{
		int RD(s);
		x+=s;
	}while(*rp);
	printf("%d",x);
}