这题string做好像简单一些

#include <bits/stdc++.h>
using namespace std;
const int N = 1e9;
#define ll long long
int main(){
    string a;
    cin >> a;
    ll x = 0 , len = a.size();
    for(int i=0;i<len;i++){
        x += a[i] - '0';
    }
    cout << x;
    return 0;
}