python/LuoGu/RuMen/P1179.cpp

#include<bits/stdc++.h>

using namespace std;
typedef long long ll;

int main() {
    ll a, b, s = 0, n;
    cin >> a >> b;
    for (ll y = a; y <= b; y++) {
        n = y;//不能改变循环变量的原值，所以要找“替身”
        while (n != 0) {
            if (n % 10 == 2) s++;
            n /= 10;
        }
    }
    cout << s << endl;
    return 0;
}