#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_skip() while(*rp++>=48)
#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);})

const t[7][8]={
//   P     C T   F
	{0,0,0,1,0,0,0,0},
	{2,0,0,1,0,0,0,0},
	{0,0,0,3,0,0,0,0},
	{2,0,0,1,4,0,0,0},
	{0,0,0,5,0,0,7,0},
	{6,0,0,1,0,0,0,0},
	{0,0,0,7,0,0,0,0},
};

int main(){
	rd_init();
	rd_skip();
	int s=0;
	int z=0;
	for(int c;c=*rp++,c!=10;){
		s=t[s][c&7];
		if(s==7){
			s=0;
			z+=1;
		}
	}
	wt1(z);
	_exit(0);
}