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

#define rd_init() char*rp=({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define wt(v) ({unsigned _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);})

int main(){
	rd_init();
	int z=0;
	int a=*rp++;
	int b=*rp++;
	if(b!='\n'){
		for(int c;c=*rp++,c!='\n';){
			z+=a!=c&&(b==a||b==c);
			a=b;
			b=c;
		}
	}
	wt1(z);
	_exit(0);
}