Compilare: user.cpp: In function ‘void Precalc()’: user.cpp:24:18: warning: variable ‘len’ set but not used [-Wunused-but-set-variable] int i,j,c[nmax],len,k,s,t; ^ user.cpp: In function ‘int main()’: user.cpp:75:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("boom.in","r",stdin); ^ user.cpp:76:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("boom.out","w",stdout); ^ user.cpp:77:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n",&N,&M); ^ user.cpp:79:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d ",&cost[i],&j); ^ user.cpp:82:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&G[i][l++]); ^