1517A - Sum of 2050 - CodeForces Solution

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

#define ll long long

void solve(){
    ll cur=2050;
    vector <ll> nums;
    ll n;
    cin >> n;
    if (n%2050>0){
        cout << -1 << endl;
        return ;
    }
    while(cur<=n){
        nums.push_back(cur);
        cur*=10;
    }
    reverse(nums.begin(),nums.end());
    int kol=0;
    for (int i =0; i<nums.size(); i++){
        while (n>=nums[i]){
            n-=nums[i];
            kol++;
        }
    }
    if (kol==0) cout << -1<< endl;
    else cout <<kol<< endl;


    return;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int64_t t;cin >> t;while (t--){solve();}
    

    return 0;
}