C++ :

#include<stdio.h>
#include<string.h>

#define M 20123

int main() {
	int f[128];
	char str[128];
	int d[128];
	int f1[128];
	int i,j,n,r;

	for(f[0]=i=1;i<128;i++) f[i]=f[i-1]*10%M;
	for(f1[0]=0,i=1;i<128;i++) f1[i]=(f1[i-1]+i*f[i-1])%M;
	while(scanf("%s",str)!=EOF) {
		n=strlen(str);
		for(i=n-1;i>=0 && str[i]=='9';i--) str[i]='0';
		if (i>=0) str[i]++; else {
			str[n]='0',str[n+1]='\0';
			str[0]='1',n++;
		}
		r=0;d[n]=0;
		for(i=n-1;i>=0;i--) d[i]=(d[i+1]+(str[i]-'0')*f[n-1-i])%M;
		for(i=0;i<n;i++) {
			r=(r+(str[i]-'0')*f1[n-1-i]*2)%M;
			if (str[i]>'2') r=(r+f[n-1-i]*2)%M;
			else if (str[i]>'1') r=(r+f[n-1-i]+d[i+1])%M;
			else if (str[i]=='1') r=(r+d[i+1])%M;
		}
		printf("%d\n",r);
	}
	return 0;
}