View Compilation Error

0_0_35507478_20335.c: In function 'main':
0_0_35507478_20335.c:14:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int i = 2;i<=sqrt(val);i++){
     ^
0_0_35507478_20335.c:14:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code