Compilare: main.cpp: In function 'int main()': main.cpp:37:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0;j<change[c-'a'].size();j++){ ~^~~~~~~~~~~~~~~~~~~~~ main.cpp:16:32: warning: ignoring return value of 'int fscanf(FILE*, const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] fscanf (fin,"%d%d\n",&r,&m); ^