foo.c: In function 'main':
foo.c:33:15: error: expected ')' before numeric constant
 a1[i] = (a1[i]10+a[j]-'0')%p1;
               ^
foo.c:34:15: error: expected ')' before numeric constant
 a2[i] = (a2[i]10+a[j]-'0')%p2;
               ^
foo.c:35:15: error: expected ')' before numeric constant
 a3[i] = (a3[i]10+a[j]-'0')%p3;
               ^
foo.c:36:15: error: expected ')' before numeric constant
 a4[i] = (a4[i]10+a[j]-'0')%p4;
               ^
foo.c:17:9: warning: unused variable 'k' [-Wunused-variable]
 int i,j,k;
         ^