foo.c: In function 'main':
foo.c:7:5: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'long int *' [-Wformat=]
     scanf("%d",&n);
     ^
foo.c:8:5: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration]
     memset(f,true,sizeof(f));
     ^
foo.c:8:5: warning: incompatible implicit declaration of built-in function 'memset'
foo.c:13:30: error: lvalue required as left operand of assignment
                 if((a[i]+a[j]=a[k])&&f[k]){
                              ^
foo.c:17:5: warning: format '%d' expects argument of type 'int', but argument 2 has type 'long int' [-Wformat=]
     printf("%d",ans);
     ^