foo.cc: In function 'void solve(char*, char*)':
foo.cc:6:13: error: 'strlen' was not declared in this scope
     int len=strlen(s);
             ^~~~~~
foo.cc:6:13: note: suggested alternative: 'mbrlen'
     int len=strlen(s);
             ^~~~~~
             mbrlen
foo.cc: In function 'int main()':
foo.cc:31:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s",s);           //s为要处理的加密字符串，答案储存在ans里
     ~~~~~^~~~~~~~

[Hydro](https://hydro.ac)提供评测服务