Compilare: main.cpp: In function 'int main()': main.cpp:20:47: warning: unused variable 'j' [-Wunused-variable] int n,cer,nx,ny,nz,nt,semn,nr,a,b,E,nr2,i,j,k,x,y,z,t,s,m,st,dr,poz1,poz2; ^ main.cpp:17:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("eq4.in","r",stdin); ^ main.cpp:18:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("eq4.out","w",stdout); ^ main.cpp:43:18: warning: 'nr' may be used uninitialized in this function [-Wmaybe-uninitialized] nr=nr*10+sir[i]-'0'; ~~^~~