text: #include <cstdio>
  #include <iostream>
  
  using namespace std;
  
  int main() {
      char yw[201], a, b;
      int i, n = 0;
  
      while ((yw[n++]=getchar()) != '\n');
      a = getchar();
      getchar();              // 中间的getchar读取用户输入的空格
      b = getchar();
  
      for (i = 0; i < n; i++) {
          if (yw[i] == a)
              cout << b;
          else
              cout << yw[i];
      }
  
      cout << endl;
      return 0;
  }
  