Compilare: user.c: In function ‘main’: user.c:52:3: warning: implicit declaration of function ‘memset’ [-Wimplicit-function-declaration] memset(fr[0], 0, sizeof fr[0]); ^ user.c:52:3: warning: incompatible implicit declaration of built-in function ‘memset’ [enabled by default] user.c:34:19: warning: unused variable ‘x’ [-Wunused-variable] int n, i, j, k, x, ch1, ch2; ^ user.c:34:16: warning: unused variable ‘k’ [-Wunused-variable] int n, i, j, k, x, ch1, ch2; ^ user.c:36:8: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result [-Wunused-result] fgets(s + 1, MAXS + 2, in); ^ user.c:37:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d", &n); ^