Compilare: main.cpp: In function 'void backt(int, int)': main.cpp:92:29: warning: self-comparison always evaluates to true [-Wtautological-compare] else if (a[i-1][j-1]==a[i-1][j-1]) ~~~~~~~~~~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:136:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("summax.in","r",stdin); ^ main.cpp: In function 'void next()': main.cpp:146:48: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] if(r++==limit) fread(sir,1,limit,stdin),r=0; ^