Help me please... tìm lỗi sai trong chương trình sau:

//Phan khai bao
#include <iostream>
namspace using std;
int a[100];
int N;
int tongam , tongduong;
int main(){
//Nhap mang
cin >> N;
cout<<"Nhap so phan tu N";
for(int i=1; i<=N; i++){
cin>>a[1];
cout<<"Nhap phan tu thu",i,":";
}
max=a[1];
for(int i:=2; i<=N; i++){
if(a[i]>max){
max=a[i];
}
for(int i=1; i<=N; i++){
if(a[i]=max){
cout<<"vitrimax="<<i;}
}
cout<<"tongduong="<<tongduong;
cout<<"tongam="<<tongam;
return 1;
}