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

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

char w[400000];

main(){
	char*rp=mmap(0l,1l<<28,1,2,0,0ll);
	RD(n);
	RD(k);
	rp+=n;
	int nw=0;
	for(int i=n;i--;){
		int h=*--rp&!nw;
		w[i]=h;
		nw+=h-w[i+k];
		if(i<k&h){
			++i;	
			int n=0;
			long d=0;
			while(++n,d=d<<8|0x30|i%10,i/=10);
			write(1,&d,n);
			_exit(0);
		}
	}
	write(1,"0",1);
	_exit(0);
}