Compilare: user.cpp: In function ‘int main()’: user.cpp:88:22: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] valhala("exp.in"); ^ user.cpp:89:24: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] ragnarok("exp.out"); ^ user.cpp:93:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&M,&N); ^ user.cpp: In function ‘char nextch()’: user.cpp:37:34: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buf,1,MAXBUF,stdin); ^