foo.cpp:1:1: error: 'include' does not name a type
 include<algorithm>
 ^
foo.cpp:4:1: error: 'string' does not name a type
 string mul(string a,string b)
 ^
foo.cpp: In function 'int sub(int, int*, int, int)':
foo.cpp:24:7: error: invalid types 'int[int]' for array subscript
 if(a[i]>b[i]) break;
       ^
foo.cpp:25:12: error: invalid types 'int[int]' for array subscript
 else if(a[i]<b[i]) return -1;
            ^
foo.cpp:29:8: error: invalid types 'int[int]' for array subscript
     a[i]-=b[i];  
        ^
foo.cpp:30:11: error: invalid types 'int[int]' for array subscript
     if(a[i]<0) a[i]+=10,a[i+1]--;  
           ^
foo.cpp:30:19: error: invalid types 'int[int]' for array subscript
     if(a[i]<0) a[i]+=10,a[i+1]--;  
                   ^
foo.cpp:30:30: error: invalid types 'int[int]' for array subscript
     if(a[i]<0) a[i]+=10,a[i+1]--;  
                              ^
foo.cpp:33:11: error: invalid types 'int[int]' for array subscript
     if(a[i]) return i+1;
           ^
foo.cpp: At global scope:
foo.cpp:36:1: error: 'string' does not name a type
 string div(string n1,string n2,int nn)
 ^