C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<iomanip>
using namespace std;
string s;
int ans=0,i;
int main(){
	cin>>s;
	for(i=0;i<s.size();i++) ans+=s[i]-48;
	cout<<ans<<endl;
	return 0;
}

Pascal :

program dxs(input,output);
var
  n,s,a:longint;
begin
  readln(n);
  s:=0;
  a:=0;
  while n>0 do
    begin
      a:=n mod 10;
      s:=s+a;
      n:=n div 10;
    end;
  writeln(s);
  readln;
end.