Compilare: user.cpp: In function ‘int main()’: user.cpp:9:28: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("per.in","r",stdin); ^ user.cpp:10:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("per.out","w",stdout); ^ user.cpp:11:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld %lld %s",&n,&k,s+1); val[0]=1; ^