depou.c: In function 'invers': depou.c:9: error: 'for' loop initial declarations are only allowed in C99 mode depou.c:9: note: use option -std=c99 or -std=gnu99 to compile your code depou.c:13: error: redefinition of 'i' depou.c:9: note: previous definition of 'i' was here depou.c:13: error: 'for' loop initial declarations are only allowed in C99 mode depou.c: In function 'main': depou.c:36: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result