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

#define rd_init() char*rp=({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#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 wt1(v) ({char wbuf[64],*wp=wbuf+sizeof wbuf;wt(v);write(1,wp,wbuf+sizeof wbuf-wp);})

typedef unsigned long ulong;

int main(){
	char rbuf[64];
	read(0,rbuf,sizeof rbuf);
	char*rp=rbuf;
	int A=rd();
	int B=rd();
	int a=rd();
	int b=rd();
	while(a%B!=b){
		a+=A;
	}
	wt1(a);
	_exit(0);
}