#include <bits/stdc++.h>

const int DIM = 1 << 20;
using namespace std;

int N, last, _next; long long answer;

class input_reader {
    private:
        FILE *input_file;
        static const int SIZE = 1 << 17;
        char buffer[SIZE]; int cursor;

        inline void advance() {
            if( ++cursor == SIZE ) {
                cursor = 0;
                fread( buffer, SIZE, 1, input_file );
            }

            return;
        }

        inline char current() {
            return buffer[cursor];
        }
    public:
        input_reader( const char *file_name, const char *file_type ) {
            input_file = fopen( file_name, file_type ); cursor = 0;
            fread( buffer, SIZE, 1, input_file );
        }

        input_reader &operator >>( int &value ) {
            value = 0;

            while( current() < '0' || current() > '9' )
                advance();

            while( current() >= '0' && current() <= '9' ) {
                value = value * 10 + ( current() - '0' );
                advance();
            }

            return *this;
        }
} input_file( "operatii.in", "r" );
FILE *output_file = fopen( "operatii.out", "w" );


int main() {

    input_file >> N;

    for( int i = 1; i <= N; i ++ ) {
        input_file >> _next;
        answer += max( _next - last, 0 );
        last = _next;
    }

    fprintf( output_file, "%lld\n", answer );

    return 0;
}