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

#define getrp() ({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd_skip() while(*rp++>=48)
#define rd() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) ({ulong _z=v;do*--wp=_z%10+48;while(_z/=10);})
#define min(a,b) (a<=b?a:b)

typedef unsigned long ulong;

int main(){
	char*rp=getrp();
	rd_skip();
	long k=rd();
	long x=rd();
	long y=x;
	long z=0;
	while(*rp){
		long a=rd();
		a+=min(y,z);
		y=min(y,z+x)+k;
		z=a;
	}
	char wbuf[64],*wp=wbuf+sizeof wbuf;
	wt(min(y,z));
	write(1,wp,wbuf+sizeof wbuf-wp);
	_exit(0);
}