View Compilation Error

0_0_24865329_30946.c:6:5: error: variably modified 'a' at file scope
 int a[maxn];
     ^
0_0_24865329_30946.c: In function 'main':
0_0_24865329_30946.c:70:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i=0;i<n;i++)
         ^
0_0_24865329_30946.c:70:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_24865329_30946.c:74:17: error: redefinition of 'i'
         for(int i=0;i<m;i++)
                 ^
0_0_24865329_30946.c:70:17: note: previous definition of 'i' was here
         for(int i=0;i<n;i++)
                 ^
0_0_24865329_30946.c:74:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i=0;i<m;i++)
         ^