C :

#include<stdio.h>
#include<string.h>
int main()
{
    int s=0,t;
    char a[10];
    scanf("%s",a);
    t=strlen(a);
    while(t--)
    {
        if(a[t]=='1')
            s++;
    }
    printf("%d",s);
    return 0;
}

C++ :

#include<bits/stdc++.h>
using namespace std;

int main() {
	string s;
	cin>>s;
	int c = 0;
	for(int i = 0;i < s.size();i++){
		if(s[i] == '1') c++;
	}
	cout<<c;
	return 0;
}

Pascal :

var a:string;
b,i,s:longint;
begin
read(a);
b:=length(a);
for i:=1 to b do
if a[i]='1' then inc(s);
write(s);
end.

Python :

a=input()
s=0
for i in range(len(a)):
    if a[i:i+1]=="1":
        s+=1
print(s)