AtCoder Beginner Contest 164---D

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;


const int MAXN=200005,MOD=2019;

int n;
char a[MAXN];
int f[MAXN],cnt[MAXN];

int main(){
	scanf("%s",a+1);
	n=strlen(a+1);
	
	ll ans=0;
	
	int cur=1;
	++cnt[0];
	
	for(int i=n;i;--i){
		f[i]=(f[i+1]+(a[i]-'0')*cur)%MOD;
		cur=cur*10%MOD;
		ans+=cnt[f[i]];
		++cnt[f[i]];
	}
	cout<<ans<<endl;
	return 0;
}