bzoj 4421: [Cerc2015] Digit Division

water problem

#include<cstdio>
char s[1<<20];
int n,m,i,a=(1e9+8)/2,t;
main(){
	scanf("%d%d%s",&n,&m,s);
	for(;i++<n;){
		t=(t*10+s[i-1]-'0')%m;
		if(!t)a=(a<<1)%int(1e9+7);
	}
	if(t)a=0;
	printf("%d",a);
}