foo.cc: In function 'void solve(char*, char*)':
foo.cc:6:11: error: 'strlen' was not declared in this scope
     int n=strlen(s);
           ^~~~~~
foo.cc:6:11: note: suggested alternative: 'mbrlen'
     int n=strlen(s);
           ^~~~~~
           mbrlen
foo.cc: In function 'int main()':
foo.cc:40:10: 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
     ~~~~~^~~~~~~~

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