View Compilation Error

0_0_15216645_23742.c: In function 'calculate':
0_0_15216645_23742.c:33:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for (int i = indexA - 1,j = 0; i>=0; --i,j++)
     ^
0_0_15216645_23742.c:33:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_15216645_23742.c:44:12: error: expected expression before 'int'
     return int(indexA);
            ^