C :

#include<stdio.h>   

int main(){  
	int x;
	scanf("%d",&x);
	
	int b = x / 100;
	int s = x / 10 % 10;
	int g = x % 10;
	
	printf("%d",b+s+g);
	
	return 0; 
} 

C++ :

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

Python :

n=int(input())
a=n//100
b=n//10%10
c=n%10
print(a+b+c)