roz.cpp: In function 'int main()':
roz.cpp:8:23: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
#define input freopen("in.txt","r",stdin)
~~~~~~~^~~~~~~~~~~~~~~~~~~~
roz.cpp:16:2: note: in expansion of macro 'input'
input;
^~~~~
roz.cpp:9:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
#define output freopen("out.txt","w",stdout)
~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
roz.cpp:17:2: note: in expansion of macro 'output'
output;
^~~~~~
roz.cpp:20:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~
roz.cpp:25:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf(" %c", &ch);
~~~~~^~~~~~~~~~~~