Compilare: main.cpp: In function 'int main()': main.cpp:28:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1;i<strlen(v);i++){ ~^~~~~~~~~~ main.cpp:16:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.in","r",stdin); ^ main.cpp:17:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("prefix.out","w",stdout); ^ main.cpp:19:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ main.cpp:22:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%s",v); ^