C :

#include<stdio.h>
int main()
{
int a,b,c,d;
scanf("%d",&a);
b=a/100;
c=(a%100)/10;
d=a%10;
printf("%d",b+c+d);
}

C++ :

#include <iostream>
using namespace std;
int main()
{
  int a,b,c,d,x;
  cin>>a;
  b=a%10;
  c=a/10%10;
  d=a/100%10;
  x=b+c+d;
  cout<<x;
  return 0;
}

Pascal :

program t21241;
var x,s:integer;
begin
  readln(x);
  s:=x div 100;
  s:=s+(x mod 100) div 10;
  s:=s+x mod 10;
  writeln(s);
end.